tl.  S.  DEPARTMENT  OF  AGRICULTUEE. 
WEATHER    BUREAU. 


STUDIES  ON  THE  DIURNAL  PERIODS  IN  THE   LOWER  STRATA 


OF  THE  ATMOSPHERE. 


Reprints  from  the  Monthly  Weather  Review,  February,  March,  April.  May,  July,  and  August,  1905. 


BY 


FRANK  HAGAR  BIGELOW.  M.  A.,  L.  H.  D., 
Professor  of  Meteorology. 


Prepared  under  the  direction  of  WILLIS  L.   MOORE,  Chief  U.  S.  Weather  Bureau. 


WASHINGTON: 

WEATHER     BUREAU. 
1905. 


f.  B.  No.  344. 

U.  S.  DEPARTMENT  OF  AGRICULTURE, 
WEATHER    BUREAU. 


STUDIES  ON  THE  DIURNAL  PERIODS  IN  THE   LOWER  STRATA 

OF  THE  ATMOSPHERE. 


Reprints  from  the  Monthly  Weather  Review,  February,  March,  April,  May,  July,  and  August,  1905. 


BY 


FRANK  HAGAE  BIGELOW,  M.  A.,  L.  H.  D., 

Professor  of  Meteorology. 


Prepared   under  the  direction  of  WILLIS   L.    MOORE,  Chief  C.  S.  Weather  Bureau. 


WASHINGTON: 

WEATHER      B  F  R  E  A  T . 

1905. 


Agm.  Dtft. 


OOITTIEIN'TS. 


Page. 
I.— The  diurnal  periods  of  the  temperature . . 

General  remarks 

Method  of  reducing  the  observations 

Results  of  the  discussion 

II. — The  diurnal  periods  of  the  barometric  pressure 

The  status  of  the  problem  of  diurnal  pressure 11 

The  diurnal,  semidiurnal,  and  tridiurnal  temperature  waves 

computed  from  the  surface  observations 12 

The  diurnal,  semidiurnal,  and  tridiurnal  temperature  waves 

in  the  lower  strata  of  the  atmosphere 14 

III. —The  diurnal  periods  of  vapor  tension,  the  electric  potential, 

and  coefficient  of  dissipation 

The  diurnal  variation  of  the  vapor  tension 

The  diurnal  variation  of  the  electric  potential  gradient . . 

The  cause  of  the  electricity  in  the  earth's  atmosphere 

The  negative  charge  of  the  earth 21 

The  periodic  variations  of  the  electric  potential  gradient  in 

the  earth's  atmosphere 

IV. — The  diurnal  periods  of  the  terrestrial  magnetic  field  and  the 

aperiodic  disturbances 

The  diurnal  periods  of  the  terrestrial  magnetic  field 29 

The  diurnal   magnetic  vectors  as  the  effect  of   the  diurnal 

temperature  waves  upon  the  redistrbution  of  the  positive 

ions  in  the  lower  strata  of  the  atmosphere 30 

The  diurnal  magnetic  vectors  in  the  polar,  temperate,  and 

tropical  zones  of  the  earth 

The  system  of  daily  magnetic  vectors  as  distinct  from  the 

hourly  vectors 

The  distribution  of  the  aperiodic  magnetic  disturbances . . . 

The  components  of  the  diurnal  wind  velocity 36 

V.— The  variable  action  of  the  sun  and  its  effects  upon   terres- 
trial weather  conditions 

Applications  to  the  problem  of  the  weather 

The  sun  a  variable  star 39 

The  synchronous  meteorological  conditions  on  the  earth.  . .        41 

VI. — General  review  of  the  status  of  cosmical  meteorology 47 

Cosmical  meteorology 47 

A  meteorological  ephemeris 47 

The  present  status  of  the  reductions 48 

The  sun  as  a  magnetized  sphere 

The  radiations  of  the  sun 49 

The  meteorological  effects  of  solar  energy 49 

The  general  organization  of  a  research  observatory . .  { 50 


Table     1.— Diurnal,   semidiurnal,   and  tridiurnal  pressure  waves 

observed  at  the  surface 12 

2. — Diurnal,    semidiurnal,     and    tridiurnal     temperature 

waves  on  three  planes,  195,  400,  and  1000  meters 12-14 

3.— Diurnal  variation  of  the  vapor  tension  at  Pare  St.  Maur, 

Paris,  50  meters  elevation 23 

4. — Diurnal  variation  of  the  vapor  tension  at  Blue  Hill, 

l!)5-meter  level 23 

5. — Diurnal  variation   of  the  vapor  tension  at  Blue  Hill, 

400-meter  level 23 

C. — Diurnal   variation  of  the  vapor  tension  at  Blue  Hill, 

1000-meter  level 23 

7. — Diurnal  variation  of  the  atmospheric  electric  poten- 
tial, Greenwich  observations  on  clear  days;  arbitrary 
scale 23 

8.— Diurnal  variation  of  the  atmospheric  electric  poten- 
tial on  rainy  and  clear  days 24 

9. — Annual   variations  of  the  atmospheric  electric  poten- 
tial, Greenwich  observations,  on  an  arbitrary  scale.         24 
10.— Hourly  values  of  the  polar  coordinates  «,  a,  jl,  at  sta- 
tions in  the  north  temperate  zone 

11. — Vectors  of  the  diurnal  magnetic  deflecting  forces 37 


ILLUSTRATIONS.  Page. 

Figure    1. — Adopted  subareasfor  collecting  the  temperature  data          2 
Figures  2  to  14. — Temperature-falls  in  the  lower  strata  from  the 
Blue  Hill  kite  observations,  1897-1902,  January 

to  December 5-7 

14  to  25. — Temperatures  in  the  free  air  of  the  lower  strata, 
Blue  Hill  kite  observations,  January  to  Decem- 
ber   8-10 

26  to  37. — Diurnal,  semidiurnal,  and  tridiurnal  components 

of  pressure  and  temperature 17-18 

38  to  49. — Diurnal  variation  of  the  vapor  tension,  A  e,  at  Pare 
St.  Maur  and  Blue  Hill  at  the  elevations  50,  195, 

400,  and  1000  meters 25 

Figure  50. — Diurnal  variation  of  the  atmospheric  electric  poten- 
tial at  Perpignan  and  Paris 26 

51. — Diurnal  variation  of  the  atmospheric  electric  poten- 
tial at  Greenwich,  1896-1900,  on  clear  days,  and 

clear  with  rainy  days 26 

a  — 
52. — Coefficient  of  electric  dissipation  q  = — j_ 27 

53. — Annual  variation  of  the  number  of  the  solar  promi- 
nences and  the  atmospheric  electric  potential 27 

54. — Comparison  of  the  diurnal  periods  of  the  temperature- 
fall,  pressure,  temperature,  vapor  tension,  electric 
potential,  and  coefficient  of  electric  dissipation ....  27 

55. — Diurnal  variation  of  the  magnetic  vectors  8,  a,  /?,  in 
latitudes  -I-  30°  to  +  60°.  «,  a  for  each  month,  ft 
for  January  and  July 33 

56. — The  annual  variation  of  the  surface  temperature  at 

Blue  Hill 30 

57. — Probable  relations  between  the  temperature  waves, 
the  streams  of  -f-  ions,  and  the  magnetic  vectors 
in  the  lower  strata  of  the  atmosphere 34 

58. — The  streams  of  -f-  ions  causing  the  diurnal  magnetic 
vectors  in  the  polar,  temperate,  and  tropical  zones 
of  the  earth 33 

59.— The  general  disturbances:  Magnetic  vectors  directed 
southward  and  caused  by  a  flow  of  -+•  ions  from 
south  to  north  in  the  air 33 

60. — The  general  disturbances:  Magnetic  vectors  directed 
northward  and  caused  by  a  flow  of  -f-  ions  from 
north  to  south  in  the  air 33 

61.— Distribution  of  the  hourly  magnetic  disturbances  at 

Washington,  D.  C.,  in  the  years  1889,  1890,  1891.  .  .  35 

62. — Distribution  of  the  great  magnetic  disturbances  in 

the  26.68-day  period  (Maunder's  data) 36 

63. — Number  of  great  magnetic  disturbances  commencing 

at  the  several  hours  (Chree's  data) 36 

64. — Retardation  of  rotation  in  different  zones  of  the  sun. .        39 

65. — Spectroheliograph  of  the  sun,  August  12,  1903,  taken 
at  the  Yerkes  Observatory,  showing  the  spots, 
flocculi,  and  general  appearance  of  the  bright  sur- 
face of  the  photosphere 43 

66.— Spectroheliograph  of  the  sun  spot  of  October,  1903, 

showing  the  calcium  flocculi  surrounding  it 44 

67.— Typical  forms  of  the  solar  prominances  or  hydrogen 

flames • 44 

68. — Variation  in  the  relative  number  of  sun  spots  in  a  11- 
year  period,  and  the  corresponding  change  in  the 
form  of  the  solar  corona 40 

69.— Examples  of  the  frequency  of  the  faculee  and  promi- 
nences at  a  minimum  (1889)  and  at  a  maximum  (1894)  41 

70. — Relative  frequency  of  the  occurrence  of  hydrogen 
flames  as  seen  on  the  edge  of  the  sun  in  a  spectro- 
scope    45 

71. — Comparison  of  the  annual  changes  in  the  prominences 
on  the  sun  and  the  temperatures  and  pressures  on 
the  earth  during  the  years  1872-1900 41 

iii 


320962 


STUDIES  ON  THE  DIURNAL  PERIODS  IN  THE  LOWER  STRATA  OF  THE  ATMOSPHERE. 


I.— THE  DIURNAL  PERIODS  OF  THE  TEMPERATURE. 


GENERAL  REMARKS. 

The  following  series  of  papers  contains  the  results  of  a 
research  into  the  periodic  diurnal  processes  that  take  place  in 
the  strata  of  the  atmosphere  within  two  miles  of  the  sea-level 
surface,  as  disclosed  by  the  data  derived  from  the  balloon  and 
kite  ascensions  made  during  the  past  ten  years.  It  includes  a 
discussion  of  the  variations  of  the  temperature,  the  pressure, 
the  vapor  tension,  the  atmospheric  electric  potential  and  coef- 
ficient of  dissipation  of  the  electric  charge,  and  the  diurnal 
periodic  action  of  the  magnetic  force.  These  subjects  have 
been  under  discussion  by  meteorologists  for  many  years,  but 
the  issue  has  been  so  indecisive  as  to  imply  that  certain  impor- 
tant terms  have  been  lacking  in  the  problems,  so  that  it  was 
impossible  to  come  to  any  definite  view  regarding  the  causes 
and  effects  in  the  physical  processes.  That  all  these  diurnal 
periods  depend  upon  the  effects  of  the  solar  radiation  in  the 
earth's  atmosphere  has  been  evident,  but  the  difficulty  of 
matching  together  the  various  lines  of  experimental  evidence 
derived  from  observations  has  been  so  great  that  no  settled 
solution  has  seemed  available.  The  additional  data  which  have 
been  recently  secured  through  observations  made  in  the  free 
air  above  the  ground  have,  however,  altered  the  point  of  view 
in  some  respects,  so  that  it  is  believed  that  the  account  to  be 
given  in  these  papers  describes  natural  conditions  more  nearly 
than  has  heretofore  been  possible. 

The  immediate  occasion  for  undertaking  this  research  con- 
sists in  the  necessity  of  deciding  upon  the  best  lines  of  work 
for  the  Mount  Weather  Meteorological  Observatory,  at  Blue- 
rnont,  Va.  The  organization  of  so  large  an  institution,  deal- 
ing with  problems  in  common  meteorology,  solar  radiation, 
atmospheric  electricity  and  magnetism,  made  it  very  important 
to  acquire  a  clear  idea  of  the  relative  values  of  the  several 
types  of  observation,  in  order  that  suitable  instruments  might 
be  installed  and  proper  observations  inaugurated.  Since  the 
effects  of  solar  radiation  involve  many  local  characteristics 
which  ought  to  be  eliminated  before  the  pure  solar  terms  can 
be  obtained,  it  was  evident  that  some  further  knowledge  of 
the  diurnal  variations  of  the  several  elements  should  be 
secured  if  possible,  at  least  to  the  extent  of  reconciling  the 
conflicting  evidence  that  the  special  lines  of  research  have 
hitherto  produced.  It  seemed  the  simplest  course  to  make  a 
study  of  the  data  furnished  by  kite  and  balloon  ascensions, 
and  for  this  purpose  the  observations  at  Berlin,1  Trappes,1 
Hald,*  and  Blue  Hill4  have  been  studied. 

In  this  paper  our  examples  will  be  taken  from  the  Blue  Hill 
data  as  more  applicable  to  the  American  meteorological  field 
than  the  European  data  can  be  without  special  consid- 
eration. It  should  be  noted  that  the  Blue  Hill  Observatory 
furnished  the  Weather  Bureau  with  certain  temperature  ob- 
servations, made  at  the  Valley  Station,  which  were  required 
in  the  proposed  discussion,  and  for  this  courtesy  our  thanks 
are  expressed. 

METHOD    OF    REDUCING    THE    OBSERVATIONS. 

In  Volume  XLIII,  Part  III,  Annual  Harvard  College  Ob- 

1  Wissenschaftlice  Luftfahrten,  1888-1898,  Berlin. 

'  Veroffentlichungen  cler  Internationalen  Kommission  f iir  wissenschaft- 
liche  Luftschiffahrt,  1901-3 

3Travaux  cle  la  Station  Franco-Scandinave  de  Bondages  Aeriens  &, 
Hald,  1902-3,  L.  T.  de  Bort. 

4  Observations  at  the  Blue  Hill  Observatory,  1901-2,  and  appendix  of 
the  observations  with  kites  1897-1902,  with  discussion  by  H.  Helm 
Clayton. 


servatory,  Table  III,  pages  166-214,  the  data  are  given  for  the 
temperatures  on  Blue  Hill  summit,  195  meters,  at  various 
heights,  and  occasionally  at  the  Valley  Station,  15  meters, 
together  with  the  hour  and  minute  of  the  observation. 

(1)  The  first  step  in  this  discussion  was  to  concentrate  this 
material  into  smaller  proportions  by  taking  the  mean  values 
where  the  kites  soared  at  about  the  same  elevation.    This  gave 
a  new  series  of  data  for  the  time,  height,  temperature  at  that 
height,  and  temperature  at  the  summit.     Corresponding  tem- 
peratures for  the  valley  at  these  times  were  extracted  from  the 
observatory  records,  at  the  request  of  the  Weather  Bureau,  so 
that  it  became  possible  to  refer  the  temperature-falls  practi- 
cally to  the  sea  level.     It  was  feared  that  any  characteristic 
effects  of  the  Blue  Hill  itself  upon  the  diurnal  temperatures, 
by  means  of  radiation  or  by  convection  currents,  might  pre- 
vent the  computed  temperatures  at  higher  elevations  from 
bringing  out  the  law  in  the  free  air  with  sufficient  purity. 

(2)  A  computation  of  the  temperature-fall  was  next  made 
for  each  time  of  observation  by  taking  the  difference  between 
the  temperature  at  the  height  and  the  valley  temperature.    A 
discussion  of  these  temperature  differences  was  preferred,  in 
order  finally  to  obtain  the  mean  temperature  at  certain  selected 
levels  for  each  hour  in  the  day,  rather  than  to  mass  together 
the  actual  temperature  readings  recorded  at  these  levels.     In 
the  former  case  the  numerical  values  are  less  scattering  than 
in  the  latter,  and  therefore  they  are  more  easily  reduced  to 
mean  values.     If  the  actual  temperatures  of  the  air,  in  the 
successive  masses  associated  with  the  progress  of  high  or  low 
areas  over  a  given  station,  are  employed  as  the  basis  of  com- 
putation, a  very  large  number  of  observations  are  required  to 
produce  correct  normal  values  in  the  several  strata.     The 
mean  temperature  falls,  on  the  other  hand,  added  to  the  nor- 
mal values  at  the  Valley  Station,  give  the  same  result  theoreti- 
cally, and  this  can  be  obtained  much  more  exactly  for  a  lim- 
ited number  of  observations  by  the  method  of  differences. 

(3)  The  first  collection  of  the  temperature  differences  con- 
tained the  data  applicable  by  simple  interpolation  to  the  levels 

15,  195,  400,  600, 3800,  4000  meters,  or  as  high  as  the 

ascension  made  its  record.     The  data  from  the  several  years, 
1897-1902,  were  collected  by  months,  so  that  for  example  all 
of  the  January  temperature-falls  were  brought  together.  They 
were  also  arranged  by  cyclonic  and    anticyclonic  areas,  so  as 
to  distinguish  between  the   cold    southward-directed   current 
and  the  warm  northward-directed  current.     The  former  covers 
generally  the  areas  lying  between  the  centers  of  the  high  and 
low  to  the  eastward  of  the  high,  with  winds  from  the  northern 
quadrants,    and    the    latter    includes   the  areas  between  the 
centers  of  the  low  and  high  to  the  eastward  of  the  low,  with 
winds  from  the  southern  quadrants.     Referring  to  the  sub- 
areas  adopted  in  my  Cloud  Report,  chart  9,  page  139,   they 
were  arranged  in  the  following  scheme,  marked  for  convenience 
H.    I=N.W.,    L.     II=N.E.,    for    southward,    L.    IH=S.W., 
H.  IV=S.E.,  for   northward.     The    subarea  for  Blue  Hill  on 
the  date  of  observation  was  scaled  from  the  Weather  Bureau 
daily  weather  maps. 

The  purpose  of  this  collection  was  to  discover  to  what  ex- 
tent the  diurnal  temperature-falls  and  corresponding  gradi- 
ents in  the  free  air  depend  upon  the  cyclonic  circulation,  that 
is  whether  the  temperature-fall  is  different  over  the  cold  cur- 
rents from  the  north  to  that  over  the  warm  currents  from  the 

I 


2 


south.  It  may  'be  stated  m  anticipation  of  the  result  that  no 
important  difference  could  be  determined  from  these  obser- 
vations. 


iSo  u  th  ward . 


High. 


17 


H 


15 


E.     L 


N.E. 


Low. 


North  wcurd . 


16 


7      15 


High. 
10  \W.H 


19      12       4 


S.E. 


13 

FIG.  1. — Adopted  subareas  for  collecting  the  temperature  data. 

(4)  In  the  next  collection  of  the  temperature-falls  the  north- 
ward data  was  kept  separate  from  the  southward  data,  both 
being  computed  independently.     A  further  concentration  was 
effected  by  interpolating  the  data  to  the  values  occurring  at 

the  hours  12  m.,  1,  2 12  p.   m.,   1, 12  m.,   for 

each  ascension,  and  bringing  together  all  the  data  occurring 
at  the  same  hour  of  the  day,  and  as  before  for  each  month  in 
the  year  at  the  adopted   200-meter  intervals.     These   tables 
give  the  respective  differences  of  temperature  at  each  hour  of 
the  day,  at  the  heights  adopted,  in  warm  and  cold  currents, 
and  for  each  month  in  the  year.     From  this  point  onward  it 
was  necessary  to  resort  to  a  graphic  construction  to  obtain 
average  values,  because  the  data  were  not  sufficiently  abundant 
at  all  hours  of  the  day,  in  each  month,  for  so  many  levels,  to 
make  the  result  reliable.     There  may  be  some  question  as  to 
the  definitive  values  of  the  results  on  this  account,  but  as  it 
was  our  purpose  to  obtain  a  provisional  idea  of  the  atmospheric 
conditions,  for  the  purpose  of  planning  further  observations  at 
Mount  Weather,  we  were  justified  in  making  as  much  as  pos- 
sible out  of  the  data  in  hand. 

(5)  The  individual  values  of  the  temperature-fall  for  each 
elevation  adopted  were  plotted  on  sheets,  keeping  each  month 
separate,  so  arranged  that  the  ordinates  are  the  differences  of 
temperature  between  that  observed  at  the  Valley  Station  and 
the  temperature  recorded  by   the  thermograph   attatched  to 
the  kite,  the  abscissas  being   the  hours  of  the  day  beginning 
at  midnight.     The  data  belonging  to  the  southward-directed, 
or  cold  currents,  were  plotted  in  black  and  the  northward,  or 
warm   currents,  in  red,  so  that  by  inspection  any  systematic 
difference  between  these  two  types  could  be  seen.     It  may  be 
stated  that  no  notable  divergence  between  the  temperature-falls  over 
the  warm  and  cold  currents  could  be  detected,  and  we  conclude  that 
the  warm  and  cold  masses  resting  on  the  ground,  on  either 
side  of  the  cyclone  center,  fall  off  by  about  the  same  gradients 
up  to  at  least  one  mile,  and  probably  to  two  miles,  in  elevation. 
These  masses  of  air,  therefore,  preserve   their  relative  inde- 
pendence in  the  lower  strata  of  the   atmosphere,  whatever 


changes  may  occur  in  their  mechanical  structure  when  pene- 
trating the  eastward  drift  of  the  higher  levels.  At  the  Valley 
Station  itself  the  actual  temperatures  were  plotted  in  the  same 
way  that  temperature-falls  were  plotted  for  the  several  levels 
lying  above  it.  Mean  lines  were  now  drawn  through  these 
several  groups,  or  points,  to  represent  as  nearly  as  possible 
the  average  values.  There  was  little  difficulty  in  doing  this 
accurately  for  the  hours  10  a.  m.  to  8  p.  m.,  where  data  were 
abundant,  but  for  the  remaining  hours  of  the  day  there  was 
more  uncertainty,  especially  in  the  winter  months,  when  the 
number  of  ascensions  was  not  great.  In  the  levels  195,  400, 
600,  800  and  1000  meters,  it  was  possible  to  construct  fairly  reli- 
able mean  curves,  but  since  the  scattering  increases  rapidly 
above  the  1000-meter  level,  it  was  not  possible  to  proceed 
directly  by  this  method  above  the  1400-meter  level. 

(6)  In  order  further  to  control  these  average  curves  and 
insure  an   accuracy  even  greater  than  could  be  obtained  by 
simple    estimation    of    the    mean    position    of    the    curves, 
the    following    process    was    employed.     For    the    hours    12 
a.  m.,   4    a.   m.,    8    a.    m.,  12  p.    m.    4    p.    in.,    and    8    p.    m., 
the  values  lying  on  these  curves    for    the    respective    hours 
were   transposed   to  another  set  of  sheets,  where   the    ordi- 
nates    are     the     temperature-falls,    and     the     abscissas    the 
month  in  the  year.     Thus  a  rough  locus  was  formed  for  12 
a.  in.  or  midnight,  so  that  the  varying  value  at  that  hour  for 
each  month   in  the  year  might  be   seen.     A  curve  was  then 
drawn  through  these   points,  smoothing  down  the  irregulari- 
ties, on  the  theory  that  the  temperature  variation  constructs 
a  comparatively  regular  curve  in  the  course  of  the  year.    This 
procedure  doubtless  tended   to  fix   six  points  on  the  diurnal 
curve  at  each  level  with    considerable   accuracy,   and   these 
adjusted  points  were  now  transferred  back  into  the  preceding 
set  of  curves  originally  derived  from  the  individual  observa- 
tions.    The  passage  from  month  to  month  in  the  way  indicated, 
allowed  us  to  bridge  over  many  gaps  in  the  kite  record  that 
could  not  otherwise  have  been  done.     The  first  set  of  curves 
was  now  readjusted   in  conformity  with  these  guiding  points 
at  4-hour  intervals.     The  adjustment  of  fragmentary  records 
by  continuous  curves  crossing  each  other  in  two  directions  as 
in  this  case,  nearly  at  right  angles,  is  not  only  expeditious  but 
usually  brings  out  results  very  close  to  the  truth,  because  the 
mutual   adjustment  of  neighboring  points  in  two  directions 
eliminates  the  merely  accidental  errors  due  to  short  and  imper- 
fect records.     This    is   especially    true   if  some  of    the  fixed 
points  are  well  established  as  in  these  observations  during  the 
afternoon  hours  of  the  warm  months  of  the  year. 

(7)  For  the  prosecution  of  this  discussion,  whose  object  it 
was  to  eliminate  the  special  local  conditions  pertaining  to  the 
Blue  Hill  summit,  it  was  necessary  to  secure  accurate  normal 
values  of  the  temperature   at   each   hour  of  the   day,  and   for 
each  month  of  the  year,  at  the  Valley  Station.     As  these  data 
were  not  in  hand  at  the  Blue  Hill  Observatory  we  proceeded 
as  follows  : 

As  stated  above,  the  normal  diurnal  curves  for  the  Valley 
Station  were  computed  from  the  data  supplied  to  the  Weather 
Bureau  at  the  times  the  kites  were  flying.  Also,  the  normal 
diurnal  temperatures  for  the  summit  were  supplied  from  the 
records  of  twenty  years,  1885-1904,  which  were  accurate.  By 
the  computations  above  described  for  the  temperature  differ- 
ences between  the  summit  and  valley,  inasmuch  as  the  amount 
of  data  was  sufficient,  we  had  reliable  corrections  which,  applied 
to  the  summit  normal  temperatures  for  each  hour,  gave  the 
corresponding  values  at  the  Valley  Station.  These  were  com- 
pared with  the  diurnal  values  obtained  on  the  days  of  kite 
ascensions,  and  from  their  combination  certain  surface  tem- 
peratures were  found  upon  which  the  temperatures  computed 
in  higher  strata  were  made  to  depend.  Any  inaccuracies  per- 
taining to  the  final  results  derived  in  this  manner  can  be 
eliminated  by  further  direct  observations,  but  it  will  require  a 


3 


very  large  number  of  additional  ascensions  to  accomplish  any 
such  purpose. 

(8)  We  can  impose  upon  this  data  yet  another  mutual  adjust- 
ment.    Up  to  this  point  the  several  curves  for  each  month 
have  been   kept  entirely  independent  of  one  another  up  to 
1400  meters,  but  they  were  now  brought  together  on  sheets, 
one  for  each  month,  by  transferring  the  several  curves  to  the 
same  set  of  axes  of  ordinates  and  abscissas.     The  successive 
curves  in  elevation  now  took  positions  appertaining  to  their 
respective  temperatures  differences.     This  can  be  seen  by  in- 
specting the  curves  of  figs.    2-13,    "Temperature-falls  in  the 
the  lower  strata,  Blue  Hill  kite  observations  1897-1902."     In 
the    lower  levels  195,  400,  600,  800  and   1000  meters,   there 
is    great     divergence     in    the    shape    of    the     curves,     but 
they     gradually    approach    a    typical    form   which    must   be 
eventually    that   of    the    temperature    curve    at    the    surface 
itself.     This  is  evident  from   the  fact  that   at    some    eleva- 
tion the  diurnal  variation  proper  of  the  temperature  ceases  to 
be  effective,  and  since  the  temperature-falls  were  measured 
from  the  surface  curve,  the  same  curve  must  appear  at  those 
levels  which  have  no  true  diurnal  variation  of  their  own.   The 
difference  between  the  surface  curve  and  the  computed  curve 
at  any  given  elevation  gives  the  variation   belonging   to  that 
level.     The  elevation  at  which  the  diurnal  variation  really  dis- 
appears for  each  month  in  the  year  was  not  known,  and  could 
not  be  determined  from  the  observations.     It  must  be  lower 
in  winter  than  in   summer,    and  I  have   merely   assumed    an 
average  of  3400  meters.     In  case  this  is  not  correct,  it  yet  is 
evident  from  the  formation  of  these  curves  up  to  1400  or  1600 
meters  that  it  has  become  a  comparatively  small  quantity  and 
that  a  change  in  the   elevation  from   3400  meters   will  have 
little  effect  upon  the  conclusions  which   we   required   in   this 
series  of  papers,  since  they  pertain  to  the  strata  up  to  only 
2000  meters. 

(9)  The  kite  ascensions  in  several  cases  extended  up  to  3000 
or  even  to  4000  meters,  and  by  studying  the  computed  table  of 
temperature-falls  it  was  not  difficult  to  select  the  temperature- 
fall  applicable  at  the  3400-meter  level  for  each  month.     These 
were  plotted  in  an  annual  curve,  and  the  smoothed  values  were 
adopted  for  further  use.    At  the  value  determined  in  this  way 
for   12  m.,  or  midday,  as   the  temperature-fall  for  the  month, 
the  mean  diurnal  temperature  curve  of  the  Valley  Station  was 
plotted,  and  it  is  seen  as  the  uppermost  curve  of  the  system 
marked  3400.     We  had  already  carried  the  other  set  of  curves 
up  to  1400  meters,  and  it  was  proper  to  suppose  that  the  gra- 
dient system  changed  by  regular  steps   between   these  two 
elevations.     A  study  of  these   curves   from   month   to  month 
will,  I  believe,  lead  to  the  conviction  that  they  are  a  very  close 
approximation  to  the  mean  temperature-fall  system  in  the  lower 
strata   which   would   be   derived   from   a  very  long  series  of 
ascensions. 

RESULTS  OF  THE  DISCUSSION. 

The  system  of  curves,  figs.  2-13,  "Temperature-falls  in 
the  lower  strata,  Blue  Hill  kite  observations,  1897-1902," 
contain  the  final  results  of  this  discussion.  The  chief  point 
of  criticism,  as  already  mentioned,  is  the  adopted  height,  3400 
meters,  at  which  the  surface  curve  should  be  located.  The 
interpolation  between  this  curve  and  the  1400-meter  curve  will 
be  a  little  different  if  the  topmost  curve  should  preferably  be 
placed  at  an  elevation  lower  or  higher  than  the  one  adopted, 
which  is  about  two  miles  above  the  summit  of  Blue  Hill.  The 
most  conspicuous  feature  of  these  curves  in  each  month  is  the 
relative  forms  of  the  curves  at  195,  400,  600,  and  800  meters, 
which  indicate  that  the  temperature-falls  are  very  different  in 
the  successive  lower  levels.  By  taking  the  differences  between 
any  two  curves  of  the  system  the  mean  temperature  gradient 
can  be  readily  computed.  Another  striking  characteristic  is 
the  persistent  inversion  of  temperatures  in  the  hours  from  10 


p.  m.  to  5  a.  m.,  especially  in  the  lower  levels  up  to  1000 
meters.  This  is  seen  by  the  ordinates  being  drawn  with  a 
positive  sign,  or  downward  on  this  scale  of  ordinates.  The 
midday  maximum  temperature-fall  can  be  seen  to  occur  at  an 
earlier  hour  in  the  lower  levels,  as  12  m.  to  1  p.  m.,  and  at  a 
later  hour  in  the  higher  levels,  as  2  to  4  p.  m.  The  maximum 
rate  of  variation  is  quite  uniformly  located  in  the  morning 
hours  at  6  to  10  a,  m.  for  rising  temperature  and  at  5  to  9 
p.  m.  for  falling  temperature.  An  examination  of  the  curves 
from  month  to  month  shows  that  there  is  a  general  increase 
in  the  amplitude  from  winter  to  summer.  At  the  same  time, 
in  the  winter  months  the  amplitude  for  the  lower  levels,  600 
to  1000  meters,  is  greater  than  for  the  upper  levels;  on  the 
other  hand,  in  summer  the  amplitude  in  the  lower  levels  is  less 
than  in  the  higher  levels.  The  transition  months,  April,  May 
and  September,  October,  have  about  equal  amplitudes  in  each 
level.  The  fact  that  this  subtle  law  has  been  deduced  by  the 
method  of  computation  employed  speaks  strongly  for  the 
efficiency  of  cross-plotted  adjustments. 

I  have  used  the  same  method  in  deducing  the  temperatures 
of  the  atmosphere  up  to  16,000  meters,  charts  78,  79,  Inter- 
national Cloud  Report,  and  in  determining  the  temperatures 
under  the  Rocky  Mountain  Plateau  at  sea  level,  chart  13, 
Barometry  Report,  and  in  other  places.  It  is  the  only  satis- 
factory way  to  adjust  broken  series  of  incomplete  data  to  an 
approximate  mean,  such  as  can  be  secured  otherwise  only  by 
a  very  great  number  of  direct  observations.  Several  other 
important  relations  will  be  found  in  the  other  papers  of  this 
series  which  tend  to  confirm  these  conclusions.  It  may  also 
be  further  noted  that  there  seems  to  be  a  semiannual  period 
in  the  positive  or  the  inversion  ordinates  in  the  morning 
hours  2  to  5  a.  m.,  as  well  as  a  rearrangement  in  the  order  of 
heights  at  which  this  is  greatest  Thus,  the  amplitude  for 
the  4  a.  m.  hour  of  the  400-meter  curve  has  a  single  period,  with 
maximum  in  February  and  minimum  in  October;  the  600-meter 
curve,  however,  has  a  maximum  in  February  and  another  maxi- 
mum in  June,  with  minima  in  April  and  October;  the  800-meter 
curve  has  two  maxima  and  two  minima  in  agreement  with  the 
600-meter  curve.  The  195-meter  curve  at  the  summit  of  Blue 
Hill  shows  that  the  temperatures  at  the  summit  and  base,  15 
meters,  do  not  vary  in  parallel,  and  hence  the  gradient  system 
referred  to  the  level  of  the  open  country  will  differ  somewhat 
from  that  referred  to  the  summit.  This  should  be  remembered 
in  the  use  of  the  gradients  of  the  Blue  Hill  Observatory  Report. 

We  have  now  obtained  the  material  necessary  for  deducing 
the  mean  (approximate)  temperatures  at  the  different  levels, 
by  merely  adding  algebraically  the  temperature-falls  to  the 
normal  temperatures  of  the  Valley  Station.  The  results  are 
given  in  the  tables,  figs.  14—25,  "Blue  Hill  temperatures  in 
the  lower  strata."  The  ordinates  of  temperature  have  been 
plotted  to  decrease  upward,  in  order  that  they  may  conform 
to  the  actual  conditions  in  the  free  air,  where  the  temperature 
diminishes  generally  with  the  height  There  are  several  re- 
sults of  unusual  interest  to  meteorology  which  appear  on  the 
face  of  these  charts.  The  first  is  the  remarkable  distribution 
of  temperature  in  the  levels  from  600  meters  upward  as  com- 
pared with  the  surface  temperatures.  In  the  winter  months — 
December  to  March,  inclusive — there  is  a  pronounced  inversion 
of  temperature  throughout  the  day,  so  that  the  night  hours, 
7  p.  m.  to  5  a.  m.,  are  warmer,  while  the  day  hours,  6  a.  m.  to 
6  p.  m.,  are  colder  than  the  mean  for  the  day  at  the  several 
levels.  It  seems  very  remarkable  that  in  the  hours  of  full 
sunshine  the  effect  of  the  radiation  on  the  temperature  of  a 
stratum  of  air  should  be  to  allow  it  to  remain  cool  rather  than 
to  heat  it.  Evidently  the  result  comes  about  indirectly,  by 
reason  of  the  fact  that  the  incoming  short-wave  radiation  has 
little  influence  directly  on  the  temperature,  because  there  is 
not  much  absorption.  These  short  waves  impinge  upon  the 
surface  of  the  earth,  which  becomes  a  radiating  body  of  low 


temperature  and  emits  long  waves.  These  are  strongly  ab- 
sorbed according  to  the  prevailing  physical  conditions,  as  the 
relative  amounts  of  dry  air  and  aqueous  vapor,  coefficients  of 
absorption  for  different  wave  lengths,  and  so  oil.  Convection 
currents  also  enter  into  the  result,  and,  indeed,  the  complex 
function  here  displayed  requires  much  careful  examination 
before  further  conclusions  can  be  stated.  The  temperatures 
diminish  generally  with  the  height  after  leaving  the  400-meter 
level,  but  the  diwrnal  period  gives  a  maximum  of  cold  at  mid- 
day, and  a  minimum  about  midnight.  In  the  summer  months, 
on  the  other  hand — June,  July,  August — the  inverted  tempera- 
ture distribution  does  not  exist  relatively  to  the  surface,  but 
the  curves  are  all  of  the  same  general  type,  with  a  maximum 
temperature  in  the  late  afternoon,  and  minimum  in  the  early 
morning.  In  the  transition  months — April,  May,  September, 
October,  November — the  diurnal  temperature  curve  has  two 
maxima,  8  a.  m.  and  8  p.  m.,  and  two  minima,  2  a.  m.  and  2  p.  m. 
The  process  of  transition  can  be  followed  in  the  several  levels 
from  month  to  month,  and  it  is  a  very  interesting  phenomenon. 
The  second  important  feature  of  these  curves  is  the  build- 
ing of  a  semidiurnal  period  in  the  temperature  at  the  eleva- 
tion 400  to  600  meters,  in  all  months  in  the  year,  with  the 
maxima  at  8  to  9  a.  m.  and  8  to  9  p.  m.  They  are  seen  very 
distinctly  represented  in  May  and  September,  where  they  are 
formed  up  to  the  very  top  of  the  diurnal  disturbance.  The 
single  diurnal  period  at  the  surface  is  replaced  by  a  double 
diurnal  wave  at  400  meters,  and  this  appears  quite  plainly  in 
every  month  except  July,  where  it  probably  is  nearly  extinct. 
In  the  higher  levels,  above  800  meters,  there  is  a  tendency  for 
the  double  periods  to  contract  the  maxima  from  the  9  a.  m., 


9  p.  m.  hours  nearer  toward  midday,  and  form  two  crests  or  a 
single  crest  near  midday,  especially  in  the  winter  months.  It 
will  be  shown  in  the  next  paper  of  this  series  that  those  super- 
posed temperature  waves,  having  their  maxima  disposed  as 
just  explained,  are  competent  to  produce  the  diurnal  variation 
of  the  barometric  pressure  in  the  single,  double,  and  triple 
components,  into  which  the  observed  pressure  at  the  surface 
is  usually  resolved  by  the  Fourier  Series  of  Harmonics.  Mr. 
Clayton  has  obtained  similar  curves  of  temperature  at  500, 
1000,  1500  meters,  as  shown  on  fig.  5  of  his  paper  on  "The 
diurnal  and  annual  periods  of  temperature." — Annual  Harvard 
College  Observatory,  Vol.  LVIII,  Part  I,  1904,  though  they  are 
composites  of  the  several  curves  really  belonging  to  different 
months  of  the  year.  It  will  be  seen  from  my  curves  that  mean 
annual  values  computed  from  observations  taken  in  all  parts 
of  the  year  are  correct  only  for  certain  limited  intervals,  in 
which  the  varying  temperatures  pass  through  such  special 
values.  Similarly,  discussions  of  all  data  depending  upon  mean 
values  made  up  in  this  way  can  have  only  a  limited  application 
in  deducing  daily  free  air  temperatures  throughout  the  year. 
This  disclosure  of  the  fact  that  the  temperature  curves  differ 
according  to  the  elevation  from  the  one  observed  at  the  sur- 
face opens  up  the  possibility  of  explaning  not  only  the  semi- 
diurnal and  triple  diurnal  barometric  waves,  but  also  the 
movements  of  the  ions  in  the  atmosphere  in  their  relation  to 
the  electric  potential  gradient,  the  coefficient  of  neutraliza- 
tion and  number  of  ions  in  the  connection  with  other  meteor- 
ological phenomena,  and  the  variations  of  the  diurnal  mag- 
netic field  in  all  latitudes  of  the  earth.  These  researches  will 
be  explained  in  the  other  papers  of  the  series. 


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10 


II.— THE  DIURNAL  PERIODS  OF  THE  BAROMETRIC  PRESSURE. 


THE  STATUS  OF  THE  PROBLEM  OF  DIDBNAL  PRESSURE. 

The  physical  relations  between  the  waves  of  temperature 
and  pressure  in  the  lower  strata  of  the  atmosphere,  together 
with  their  influence  upon  the  electrical  and  the  magnetical 
fields  in  the  air,  have  formed  subjects  of  constant  investiga- 
tion during  the  past  forty  years,  but,  unfortunately,  without 
any  satisfactory  results.  In  my  International  Cloud  Report, 
Weather  Bureau,  1898,  chapter  9,  some  account  of  the  problem 
was  given,  and  an  attempt  was  made  to  throw  some  additional 
light  upon  the  subject.  The  principal  point  brought  out  was 
the  fact  that  there  is  a  very  close  connection  between  the  vari- 
ation of  the  pressure  and  the  magnetic  fields  over  the  earth, 
although  I  was  unable  to  show  what  the  physical  process  is 
which  unites  them.  The  papers  of  this  series  are  supplemen- 
tary to  that  investigation,  and  they  show  that  two  important 
elements  have  been  lacking  in  the  terms  of  the  problem;  name- 
ly, the  variation  of  the  temperature  with  the  height,  and  the 
existence  of  streams  of  ions  or  free  charges  of  electricity  in  the 
-lower  atmosphere.  Without  them  it  was  not  possible  to  ex- 
plain the  connection  between  the  several  types  of  observed 
phenomena. 

There  have  been  in  general  two  lines  of  attack  upon  the 
problem  of  the  coexistence  of  the  single,  the  double,  and  the 
triple  barometric  waves,  as  determined  by  the  harmonic  com- 
ponents: First,  that  they  are  due  directly  to  an  effect  of  the 
temperature  upon  the  pressure  by  a  change  in  the  density  of 
the  lower  strata  of  air;  and  second,  that  a  dynamic-forced 
wave  is  generated  chiefly  by  solar  radiation  acting  in  the  upper 
strata  of  the  atmosphere.  However,  it  has  not  been  possible 
to  associate  the  surface-temperature  wave  with  the  semidiurnal 
and  the  tridiurnal  waves  of  pressure,  because  it  has  been 
assumed  that  the  surface-temperature  wave  extends  with  the 
same  periodic  phase  into  the  lower  strata.  We  have  shown 
in  the  preceding  paper  that  this  is  not  the  case,  and  that  there 
is  now  sufficient  reason  for  reopening  the  problem  at  this 
place.  Regarding  the  solution  by  a  dynamic-forced  wave,  it 
has  become  more  evident1  from  the  studies  of  the  absorption 
of  the  solar  radiation,  by  means  of  the  bolometer  and  the  ac- 
tinometer,  that  the  solar  energy  can  not  build  up  temperature 
and  dynamic  waves  in  the  upper  strata,  because  the  solar  radi- 
ation is  of  such  short  wave  lengths  as  to  traverse  the  earth's 
atmosphere  without  general  absorption.  The  outgoing  radia- 
tion of  much  longer  wave  lengths  from  the  earth's  surface 
does,  however,  suffer  absorption,  so  that  such  dynamic  effects 
must  belong  to  the  lower,  rather  than  to  the  higher,  strata  of 
the  atmosphere.  Further  studies  have  been  made  by  the 
Austrian  meteorologists,  Margules,  Hann,  and  Trabert,  in  a 
series  of  interesting  papers1,  since  the  year  1898. 

It  may  be  remarked  that  these  discussions  are  confined  to 
an  account  of  the  double  period,  apart  from  its  natural  com- 

1  See  Monthly  Weather  Keview,  December  1902,  figs.  3  and  4. 

2Ueber  die  tagliche  Drehung  der  mittleren  Windrichtung  und  iiber 
eine  Oscillation  der  Luftmassen  von  halbtagiger  Periode  auf  Berggipfeln 
von  2  bis  4  km.  Seehohe.  J.  Hann.  Wien.  1902. 

Same  in  lleteorologische  Zeitschrift.     Oktober,  November,  1903. 

Die  Theorie  der  taglichen  Luftdruckschwankung  von  Margules  und 
die  tagliche  Oscillation  der  Luftmassen.  W.  Trabert.  Met.  Zeit.  No- 
vember, December,  1903. 


bination  with  the  single  and  triple  periods.  Suitable  periodic 
variations  of  the  coefficients,  in  latitude  and  longitude,  were 
not  to  be  found  in  the  observations  at  the  surface  stations, 
nor  at  the  mountain  stations,  and  there  was  no  data  derived 
from  the  free  air  levels.  Contact  with  the  ground  at  low  levels, 
or  at  high  elevations,  seems  to  have  destroyed  the  actual 
temperature  waves  found  in  the  free  air  at  400  meters  and  up- 
ward. It  will,  no  doubt,  now  be  possible  to  adapt  these  admir- 
able mathematical  studies  of  the  Fourier  series,  as  modified  by 
the  deflecting  force  of  the  earth's  rotation  and  by  friction,  to 
the  new  temperature  data  pertaining  to  the  strata  up  to  3000 
meters  elevation  in  the  free  air. 

In  order  to  place  before  the  reader  a  brief  summary  of  the 
facts  of  the  barometric  pressure  waves  which  are  to  be  ex- 
plained, the  following  extract  is  quoted  from  my  Cloud  Report, 
pages  458,  459. 

Analyzing  the  observed  barometric  pressure  by  the  harmonic  series, 
A  B  =  a,  sin  (At  +  x)  +  a,  sin  (Ai  +  Zx)  +  a,  sin  (A3  +  3x),  and  discus- 
sing the  constants  in  respect  to  the  observations,  it  is  noted:* 

1.  The  normal  value  of  the  amplitude  of  the  single  daily  oscillation  c^ 
is  contained  within  the  limits  0.00  and  0.50  mm.    It  is  one-fourth  to  one- 
half  the  amount  of  a.,;  its  range  is  wide,  being  two  or  three  times  the 
normal  value ;  it  is  very  different  at  neighboring  stations,  and  on  the 
same  parallel  of  latitude;  it  has  greater  amplitudes  in  mountain  valleys, 
but  smaller  on  the  seacoast  and  in  higher  latitudes;  it  shows  a  reversal 
of  phase  in  the  polar  regions,  also  above  a  certain  neutral  plane  at  a 
given  elevation  from  the  ground,  produced  by  interference  with  the  ther- 
mic wave;  it  has  a  yearly  period,  with  maxima  in  June  in  higher  lati- 
tudes, and  in  March  and  September  on  the  equator. 

2.  The  normal  value  of  the  phase  A,  is  near  0°,  where  x  is  counted 
from  midnight,  and  is  the  hour  angle;  it  varies  widely,  from  277°  to  55°; 
a,  and  Al  must  have  a  general  and  a  local  cause.     The  general  cause 
varies  with  the  latitude  and  also  in  the  year;  the  local  cause  varies  with 
the  minor  convection  currents,  and  depends  upon  all  the  meteorological 
features  which  tend  to  produce  local  convection. 

3.  The  amplitude  of  the  double  daily  wave,  a,,  is  the  principal  term, 
and  covers  the  limits  0.00  to  1.00  mm.  of  pressure.     Its  range  is  very 
narrow;   it  decreases  regularly  with  the  height  proportionally  to  the 

T> 

pressure  s™- ;  it  is  very  constant  over  the  entire  earth  up  to  latitude 

55°;  it  varies  with  the  latitude  by  a  formula  which  requires  an  inversion 
of  phase  in  the  polar  regions;  it  has  a  distinct  variation  with  the  year, 
but  exhibits  the  following  peculiarity,  namely,  that  while  the  maximum 
insolation  is  in  January  at  perihelion,  the  maximum  of  the  semidiurnal 
wave  is  at  the  equinoxes  in  March  and  September;  also  the  fact  is 
remarkable  that  the  sun  in  one  hemisphere  does  not  change  the  ampli- 
tude of  the  wave  in  the  other  hemisphere;  it  combines  with  the  single 
"thermic  "  wave,  but  it  is  not  controlled  by  it  to  any  appreciable  extent; 
it  is  smaller  on  seacoasts,  islands,  and  on  mountain  tops,  and  is  dimin- 
ished a  little  by  land  and  sea  breezes;  it  is  very  large  in  mountain 
valleys. 

4.  The  normal  value  of  the  phase  of  the  double  diurnal  wave  A,  is 
155°,  corresponding  to  9h  50°"  a.  m.;  its  range  is  very  small,  148°  to  163°; 
it  diminishes  a  little  with  the  height,  is  retarded  to  145°  in  higher  lati- 
tudes, varies  a  little  with  the  year,  though  in  an  opposite  sense  in  the 
two  hemispheres,   and  it  is  very  independent  of  local  meteorological 
influences. 

5.  The  amplitude  of  the  triple  diurnal  wave,  a,,  is  a  very  small  quan- 
tity, being  generally  less  than  0. 10  mm.  pressure.     It  diminishes  a  little 
with  the  latitude;  its  yearly  period  is  very  marked,  and  has  maxima  in 
winter  and  summer  in  both  hemispheres,  with  minima  at  the  equinoxes; 
its  maximum  is,  however,  in  June,  when  the  earth  crosses  the  sun's 
equator,  and  not  in  July,  when  the  heat  is  greatest  in  the  Northern 
Hemisphere. 

6.  The  phase  of  the  triple  daily  period,  A3,  has  a  normal  value  of  355°, 
with  very  small  range,  and  with  a  small  but  very  well  marked  yearly 
period. 

11 


12 


THE    DIUBNAL,    SEMIDIURNAL,    AND    TRIDIURNAL    PRESSURE    WAVES    COM- 
PUTED   FROM    THE    SURFACE    OBSERVATIONS. 

We  can  obtain  the  three  component  pressure  waves  from 
the  Weather  Bureau  observations  by  employing  the  data  con- 
tained in  Mr.  P.  C.  Day's  paper,  prepared  by  direction  of 
Brig.  Gen.  A.  W.  Greely,  "  Diurnal  Fluctuations  of  Atmos- 
pheric Pressure  at  twenty-nine  selected  stations  in  the  United 
States,  Washington,  1891."  The  tables  give  the  local  hourly 
corrections  to  the  daily  mean  pressure;  hence  by  changing  the 
signs,  we  obtain  /)5,  the  variations  of  the  pressure  for  each 

TABLE  1. — Diurnal,  semidiurnal,  and  tridiurnal  pressure  waves  observed  at 
the  surface.     Unit  =.  0.001  inch  mercury. 


S 

January. 

February. 

March. 

April. 

9 

H 

AB. 

I. 

II. 

III. 

A.B. 

I. 

II. 

III. 

AJJ. 

I. 

II. 

III. 

A.B. 

i. 

II. 

III. 

12a 

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—  1 

+  1 

c 

+  1 

—  1 

+  3 

—  : 

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—  1 

+  4 

C 

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+  I 

0 

1 

—  3 

+  2 

—  £ 

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—  2 

+  2 

—  7 

+! 

C 

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—  6 

+1 

0 

+  3 

—  S 

0 

2 

—  5 

+  4 

—IE 

-[-l 

—  £ 

+  8 

—14 

—  S 

—12 

+3 

—  4 

+  7 

—11 

0 

3 

—  6 

f  4 

—  1{ 

+£ 

^ 

+  c 

—17 

-H 

—  i 

+K 

—16 

+2 

—  6 

+12 

—11 

4 

—  6 

+  7 

-1J 

C 

—  7 

+  8 

—16 

—  3 

+13 

—16 

0 

—  2 

+15 

—  1 

5 

—  4 

+10 

—  £ 

—  £ 

< 

+10 

—11 

—  i 

+  « 

+16 

—10 

0 

+  4 

+16 

—  1! 

6 

+  1 

+11 

—  S 

+  2 

+11 

—  4 

—  j 

+  S 

+15 

—  5 

—2 

+12 

+17 

—  6 

0 

7 

+10 

+  8 

+  £ 

—  '. 

+10 

+13 

+  4 

—  ' 

+16 

+14 

+  4 

—  ; 

+20 

+17 

+  3 

0 

8 

+20 

+  8 

+12 

C 

+20 

+  a 

+12 

__] 

+24 

+12 

+  12 

+26 

+15 

+  11 

0 

9 

-j-i$ 

+  7 

+17 

+4 

+29 

+  a 

+17 

•H 

+29 

+11 

+17 

+i 

+29 

+18 

+  16 

0 

10 

+31 

+  7 

+1? 

+6 

+32 

+  7 

+19 

+29 

+  8 

+18 

+3 

+27 

+10 

+  17 

0 

11 

+24 

+  5 

+14 

+5 

+23 

+  4 

+14 

_l_j 

+  19 

+  8 

+12 

+2 

+  17 

+  6 

+12 

Up 

+  2 

+  1 
1 

+  1 

+  6 
11 

+  1 

+  3 

+1 

+  4 

t 

+  4 

( 

+  5 

A 

+  1 

+  S 

—  1 

2 

—25 

-  3 

-15 

' 

-22 

—  3 

—14 

—20 

—  6 

—12 

t 

—17 

—  6 

—  i 
—11 

0 

3 

-24 

—  5 

—15 

—4 

—27 

—  3 

—17 

—  \ 

-27 

—  9 

—16 

—2 

—26 

—10 

—16 

0 

4 

—20 

—  7 

—13 

C 

—25 

—  8 

—16 

—  i 

—28 

—12 

—16 

1 

—30 

—14 

—16 

o 

5 

—14 

—  9 

—  9 

+4 

—18 

—10 

—11 

+8 

—25 

—16 

—10 

+1 

—28 

—16 

-12 

0 

6 

—  7 

—10 

—  a 

+6 

—  9 

—11 

—  4 

+6 

—17 

—15 

—  5 

+i 

—22 

—17 

—  5 

0 

7 

0 

-11 

+  5 

+fi 

—  2 

—12 

+  4 

+6 

—  9 

—15 

+  4 

—14 

—16 

+  3 

8 

+  4 

—  8 

+  12 

( 

+  4 

—  9 

+11 

+1 

-  1 

—13 

+12 

( 

—  5 

—15 

+11 

J 

9 

+  5 

—  7 

+17 

+  5 

—  9 

+17 

—a 

+  4 

—13 

+17 

( 

+  2 

—14 

+16 

0 

10 

+  4 

—  7 

+18 

-7 

+  5 

—  9 

+14 

—5 

+  6 

—10 

+18 

5 

+  6 

—11 

+17 

0 

11 

+  3 

—  7 

+14 

—4 

+  4 

—  3 

+14 

» 

+  5 

—  5 

+12 

—5 

+  6 

—  6 

+  12 

0 

12 

i 

—  1 

+  1 

« 

+  1 

—  1 

+  3 

—  1 

+  3 

—  1 

+  4 

° 

+  4 

—  1 

+  S 

0 

May. 

June. 

July. 

August. 

12a 

—  1 

-5 

+  4 

—  0 

—  1 

+  6 

+ 

( 

-6 

+  6 

—  1 

—  6 

+  5 

0 

1 

—  4 

—  1 

—  3 

—  4 

—  S 

—  1 

—  2 

—  5 

0 

—  3 

—  1 

—  2 

0 

2 

—  7 

+  3 

c 

— 

—  7 

+  2 

—  7 

_ 

—  5 

+  2 

—  6 



—  6 

+  3 

—  8 

—1 

3 

—  8 

+  8 

—14 

—  * 

—  8 

+  6 

—22 



—  5 

+  7 

—11 



—  6+6 

—11 

1 

4 

—  4 

+12 

—15 

— 

—  5 

+11 

—14 



—  2 

+11 

—13 

—  3   +12 

—14 

—1 

5 

+  4 

+15 

—11 

+  3 

+13 

—11 

+  1 

+  3 

+  14 

—12 

_i_ 

+  4   +15 

—11 

0 

6 

+11 

+17 

—  6 

+  13 

+17 

—  6 

+2 

+11 

+15 

—  7+3 

+  14'  +17 

—  5 

+2 

7 

+22 

+18 

+  3 

+ 

+20 

+  17 

+  1 

+ 

+19 

+16 

+  1     +2 

+20    +18 

+  1 

+1 

8 

4-27 

+17 

+10 

+26 

+  17 

+  8 

+24 

+17 

+  7|        ( 

+26    +18 

+  8 

0 

9 

+29 

+15 

+14 

+29 

+16 

+13 

+27 

+15 

+  12 

+28 

+15 

+  13 

0 

10 

+27 

+14 

+14 

— 

+27 

+  15 

+12 

— 

+25 

+10 

+16 



+26 

+11 

+16 

—1 

11 

+19 

+  11 

+10 

—  * 

+20 

+11 

+11 

—  ; 

+19 

+  9 

+11 



+20 

+10 

+11 

—1 

12 

+  9 

+  6 

+  4 

— 

+11 

+  7 

+  6 

—  ; 

+  11 

+  5 

+  6 

+  11 

+  7 

+  5 

—1 

1 

—  1 

+  2 

—  3 

+  2 

+  2 

—  1 

+1 

+  2 

+  1 

0 

_i_ 

—  1 

+  1 

—  2 

0 

2 

—11 

—  2 

—  9 

—  7 

—  2 

—  7 

+2 

—  2 

—  6 

+S 

—  9 

—  8 

—  8 

+2 

3 

—20 

—  7 

—14 

_|- 

—16 

—  6 

+12 

-1-2 

-16 

—  7 

—11 

+2 

—16 

—  6 

—11 

4-1 

4 

—25 

—10 

—15 

—22 

—  9 

—14 

-H 

-23 

—10 

—13 

—24 

—10 

—14 

0 

5 

—26 

—15 

—11 

—25 

—14 

—11 

—26 

—  H 

—12 

—26 

—15 

—  11 

0 

6 

—22 

—15 

-  6 

— 

-25 

—17 

—  6 

—  <t 

-24 

—16 

—  7 



—24 

—20 

—1 

7 

—17 

—18 

+  3 

—19 

—18 

+  1 

—  1 

—18 

—18 

+  1 



—18 

—18 

+  1 

—1 

8 

—  8 

—17 

+10 

— 

—11 

—17 

+  8 

—  I 

—10 

—17 

+  7 

—10 

-17 

+  8 

—1 

9 

—  2 

—16 

+  14 

i 

—  3 

—17 

+13 

+1 

—  3 

—16 

+12 

i 

—  3 

—16 

+13 

0 

10 

+  1 

—13 

+14 

i 

+  1 

—15 

+14 

+2 

+  6 

—13 

+16 

+; 

+  1 

—17 

+  16 

+2 

11 

+  1 

—10 

+10 

4- 

+  2 

—11 

+11 

+2 

+  2 

—11 

+11 

+  1 

—11 

+11 

+  1 

12 

—  1 

—  5 

+  4 

i 

0 

—  7 

+  6 

+1 

0 

—  6 

+  6 

0 

—  1 

—  6 

+  6 

0 

September. 

October. 

November. 

December. 

12a 

0 

—  4 

+  5 

_, 

0 

—  3 

+  i 

0 

0 

0 

—  1 

+1 

0 

0 

—  1 

+  1 

1 

—  2 

0 

—  3 

( 

-3+2 

+2 

—  2 

+  3 

—  9 

+4 

—  2 

+  3 

—10 

+B 

2 

—  5 

+  4 

—10 

+1 

-6+6 

1J 

+2 

—  5 

+  4 

—14 

+5 

—  4 

+  3 

—14 

+7 

3 

—  6 

+  8 

-15 

+1 

—  6    +10 

-16 

+1 

—  5 

+  7 

—15 

+3 

—  5 

+  6 

-15 

+4 

4 

—  3 

+  14 

—17 

0 

—  2    +13 

-15 

0 

—  4 

+  9 

—13 

(i 

—  5 

+  9 

—12 

-2 

5 

+  4 

+15 

—11 

0 

+  4   +16 

—10 

—  2 

0 

+12 

—  8 

2 

+10;  —  7 

—5 

6 

+  13 

+17 

J 

0 

+12 

+  17 

—  j 

t 

+  7 

+15 

—  2 

—  ( 

+  4 

+11!  —  1 

—6 

7 

+21 

+17 

-|~  4 

I 

+21 

+17 

+  6 

2 

+15 

+  11 

+  6 

1 

+  12 

+  9+6 

—  3 

8 
9 

+27 
+30 

+18 
+16 

+10 
+14 

( 

+28 
+31 

+  16 
+  13 

+  12 
+16 

9 

+2 

+24 
+30 

+11 
+  9 

+12 
+17 

+'. 

+21 
+29 

+  9; 

+  8 

+11 
+16 

+  1 
+5 

10 

+28 

+12 

If 

+1 

+29 

+  11 

+16 

+2 

+29 

+  7 

+17 

+5 

+30 

+  6 

+  17 

+7 

11 

+21 

+  8 

+12 

1 

+19 

+  8 

+10 

+1 

+  16 

+  3 

+  10 

+17 

+  3 

+  10 

+4 

12  p 

+10 

+  5 

+  5 

0 

+  6 

+  3 

+  3 

0 

—  2 

—  1 

—  1 

( 

—  2 

+  1 

1 

2 

1 

—  2 

+  1 

—  3 

0 

—10 

—  1 

—  7 

j 

—15 

—  2 

—  9 

—17 

—  2 

-10 

• 

2 

—14 

—  4 

—10 

0 

—21 

—  6 

—13 

5 

—23 

—  3 

—14 

—  ( 

—24 

—  4 

—14 

.. 

3 

—24 

—  9 

—15 

0 

—27 

—  9 

—16 

—2 

-25 

—  8 

-15 

—24 

—  B 

—15 

—  3 

4 

—31 

—13 

-17 

—1 

—28 

-13 

—  15 

0 

-22j  —10 

—13      +1 

—18  —  7 

—12 

5 

—26 

—15 

—11 

0 

—23 

—15 

—10 

+2 

—16   —12 

—  8     +4 

—11    —  9 

_  7 

+5 

6 

—21 

—18 

—  4 

+1 

-17 

—16 

—  3 

+2 

-10 

—12 

-  2      +5 

—  5  —11 

—  1 

+-7 

7 

-18 

—18 

+  4 

+1 

—10 

-17 

+  6 

+1 

-  8 

—12 

+  6|     +3 

—  1 

—11 

+  6 

+4 

8 

—  8 

—18 

+  10 

0 

—  4 

—  15 

+12 

0 

—  1 

—13 

+12,        0 

+  1 

—  8 

+11 

—2 

9 

—  2 

-16 

+14 

0 

0 

—14 

+16 

—2 

+  3 

-10 

+17 

—4 

+  1 

—  8 

+  16 

—  5 

10 
11 

+  1 
+  2 

—14 
—10 

+15 
+  12 

0 
0 

+  2 
+  1 

-12 
-  7 

+16 
+10 

—2 
2 

+  4 
+  3 

—  7 
—  5 

+  17 
+10 

-6 
-2 

+  3—5 

+  3—8 

+17 
+10 

—6 

12 

0—4 

+  6 

—1 

0 

-  3 

+  3 

0 

0 

0 

+  1 

Oj       0 

—  1 

+  1 

hour,  which  are  to  be  resolved  into  three  harmonic  components 
by  the  Fourier  series.  Five  stations  were  selected  which  are 
naturally  comparable  with  Blue  Hill,  being  located  at  short 
distances  above  sea  level,  Boston,  New  York,  Washington,  Buf- 
falo, and  Cleveland.  The  mean  variation  at  each  hour  was  com- 
puted for  these  stations,  and  it  appears  in  the  column  of  the 
Table  1  marked  AB,  for  each  month  of  the  year.  In  order 
that  it  might  be  learned  whether  the  continental  plateau  sta- 
tions produce  the  same  results,  the  following  stations,  Bis- 
marck, St.  Louis,  Dodge,  Denver,  and  Salt  Lake  City,  were 
computed  in  the  same  manner  throughout  the  year.  Since  no 

TABLE  2. — Diurnal,  semidiurnal,  and  tridiurnal  temperature  waves,  on  three 

planes.    •  Unit  — /  degree  Fahrenheit. 

JANUARY. 


£ 
§ 

195  meters. 

400  meters. 

1000  meters. 

Sums. 

« 

AT. 

I. 

II. 

III. 

AT. 

I. 

II. 

III. 

AT. 

I. 

II. 

III. 

I. 

n. 

III. 

12a.  .  . 

+0.7 

+1.7 

—1.0 

-0.0 

-1.8 

-0.5 

—1.8 

0.0 

-3.4 

-4.8 

+0,fi 

+0,8 

-3.6 

—  1  7 

+0.8 

1 

+1  5 

+2  5 

0  9 

+0  * 

2 

+2  0 

-4-2  7 

0  8 

-t-0  1 

3  

+2.5 

+3.0 

-0.5 

0.0 

—1.3 

—0^6 

—  i!s 

-0.1 

—3.8 

—3,7 

+0  1 

—  0  f, 

-  0.  1  —2.  2 

—0.3 

4 

+2  7 

+3  1 

0  3 

0  ] 

5  

+  2.9 

+2.9 

+0  1 

0  1 

+  1  9 

+1  4 

+0  4 

-t-O  1 

1  y 

6... 

+2.9 

+2.5 

+0  4 

0  0 

-t-3  0 

+1  5 

J_t     Q 

402 

0  (1 

7.. 

+2  8 

+2  0 

+0  8 

0  0 

+3  5 

+  1  5 

+  1  9 

8  

+2.7 

+1.5 

+  1.2 

0.0 

+3.6 

+1.4 

+2.2 

n.u 

+2.1 

+  1.3 

0.0 

+fl.f 

+  4.2 

+  3  4 

0.8 

9  

+  1.8 

+0.1 

+1.5 

+  0.i 

+3  2 

+1.3 

+2.1 

—0.2 

+3.0 

+2.S 

+0.1 

+  0.4 

+  3.9 

+3  7 

+  0.4 

10  

+0.4 

-0.2 

+0.5 

+0.1 

+2.2+1.1 

+  1.3 

—  o.s 

+3.6 

+3,2 

+  0  4 

0  C 

+  4.1 

+  ?,  f 

-0.1 

HP  

-1.3 

—1.0 

-0.3 

0.0 

+1.0'  +0.9 

+0.2 

—0.1 

+4.1 

+3.9 

-10,4 

-0,2 

+  3.8 

+  0  3 

—0.3 

12  

—2.7 

—1.6 

—1.0 

-0.1 

-0.  8  —0.  2 

—1.3 

-0.8 

+4.5 

+4,1 

+0,6 

-0  '1 

+  2.3 

-1  7 

—0.6 

1  

-3.3 

—2.3 

-0.9 

—0.1 

-1.8 

0.0 

—1.9 

+  0.  1 

+4.6 

+4,2 

+0,4 

fl  C 

+  1.9 

—2  4 

0.0 

2  

—3.5 

—2.7 

—0.8 

O.I 

-2.  2  -0.  3 

-2.1 

+0.5 

+4.4 

+4  0 

+0,  ? 

+0  1 

i     1.0—2.7 

40.4 

3  

—3.5 

-3.0 

-0.5 

0.0 

-2.  3  -0.  6 

—1.8 

+0.1 

+4.0 

+3.4 

+0.1 

+  0.5 

-  0.  :i 

—2.2 

+  0.6 

4  

—3.3 

-3.0 

—0.3 

0.0 

-1.9—1.0 

-0.fi 

O.I) 

+3.6 

+i>  5 

+  0  3 

+0  P 

-1.5 

—0.9 

+  0.8 

5  

-2.8 

—3.1 

+0.1 

+0.2 

-1.1  -1.3 

+0.4 

—0,2 

+  2.2 

+1  fi 

+  0  ? 

+0  4 

-2.8 

+  0  7 

+  0.4 

6  

—2.2 

-2.7 

+0.4 

+  0.1 

-0.  4  —1.  5 

+  1.3 

-0,2 

+  0,4 

+0  5 

—n  i 

0  (1 

-3.7 

+  1.6 

—0.1 

7  

—1.3 

—2.1 

+0.8 

0.0 

1-0.3—1.5 

+  1.9 

—0.1 

—1.0 

—0.7 

—0.1 

—0.2 

^4.3 

+2,6 

—0.3 

8  

-0.3 

—1.4 

+  1.2 

-0.1 

!  0.  8  -1.  1 

+2.2 

—  O.H 

—2.1 

—1.9 

0.0 

—0.2 

—  44 

+  3  4 

—0.6 

9  

+0.1 

—1.3 

+1.5 

—0.1 

+0.9 

—1.3 

+2.1 

+0  1 

-2  a 

—  9,  9 

+0  1 

0  0 

—  5.4 

-1-3.7 

0.0 

10  

+0.5 

0.0 

40.5 

0.0 

+0.4 

-1.1 

+1.3 

+0.2 

-3.2 

—3.8 

+0.4 

+  0.2 

—  4.9+2.2 

+  0.4 

11.... 

+0.7 

+1.0 

-0.3 

0.  U 

-0.6 

-0.9 

+0.2 

+0.1 

—3.4 

-—1.3 

+  0.4 

+  0.5 

—  4.  2j+0.3 

40.  6 

12  

+0.7 

+1.7 

—1.0 

0.0 

-1.8 

—0.5 

—1.3 

0.  C 

—3.4 

—4.8 

II.  (I 

+0.8 

—  3.  6|—  1.  7 

+0.8 

24.7 

24.2 

21.6 

FEBRUARY. 


12  a... 

+1.2 

+2.0 

—0.7 

—0.1 

-0.8 

+0.6 

—1.2 

—0.2 

-3.2 

—2.8 

-0.1 

—0.3 

-0.2 

—2.  0—0.  6 

1  

+  1.7 

4-2.6 

—1.0 

+  0.1 

+0.1 

+1.1 

—1.2 

+  0.2 

-2.9 

-S.I 

+0.2 

—0.1 

-0.3 

—2.0  40.  2 

2  

+2.2 

+3.1 

—1.1 

+  0.2 

+1.0 

+1.4 

—1.0 

n.  i 

-2.7 

—3.1 

+0.1 

o.  :-; 

+  1.4 

-2.041.1 

3  

+2.6 

+3.4 

—1.0 

+0.2 

+  1.7 

+  0.9 

—0.7 

(l.  ;, 

-2.4 

—2.7 

-0.1 

(i.  -i 

+  1.6 

—1.8  +1.1 

4  

+2.7 

+3.5 

-0.8 

0.0 

+2.3 

+1.8 

—0.5 

0.0 

-2.1 

—2.3 

—0.2 

40.4 

+  3.5 

-1.5 

+  0.4 

5  

+3.0 

+3.3 

—0.2 

—0.1 

+  2.7 

+2.8 

—0.1 

0.0 

—1.6 

-1.8 

—0.2 

+0.  4 

+  4.3 

—0.5 

40.3 

6  

+3.1 

+2.8 

+  0.5 

—0.2 

+3.1 

+2.7 

+0.5 

—0.1 

-1.0 

—1.3 

+0.2 

+  0.1 

+  4.2 

+  1.2 

-0.2 

7  

+2.9 

+2.3 

+0.9 

—0.3 

+3.3 

+2.3 

+1.1 

—0.1 

—0.3 

-0.4 

+0.3 

—0.2 

+  4.2 

+2.3 

—0.6 

8  

+  2.7 

+2.1 

+0.7 

-0.1 

+3.5 

+2.2 

+1.5 

-0.2 

+  0.5 

+0.4 

+0.4 

n.:; 

+  4.7 

+2.6 

—0.6 

9  

+1.8 

+0.7 

+1.0 

+0.1 

+3.3 

+1.5 

+  1.6 

+  0.2 

+  1.3 

+0.9 

+0.5 

—0.1 

+  3.1 

+3.  1  +0.  2 

10  

+0.7 

—0.1 

+  0.6 

+0.2 

+2.3 

+  0.7 

+  1.0 

+0.6 

+2.2 

+1.5 

+0.4 

+0.3 

+  2.1 

+2.0 

+1.1 

11  

-0.7 

—0.9 

0.0 

+0.2 

+0.4 

0.0 

-0.1 

+0.5 

+2.7 

+2.2 

+0.1 

+0.4 

+  1.3 

0.0 

+  1.1 

12  p.... 

-2.5 

—1.8 

—0.7 

0.0 

-1.6 

—0.4 

—1.2 

0.0 

+3.1 

+2.8 

-0.1 

^0.4 

+  0.6 

—2.0 

+  0.4 

1  

-3.6 

—2.5 

—1.0 

—0.1 

-2.4 

—1.2 

—1.2 

0.0 

+  3.2 

+2.6 

+0.2 

+0.4 

-  1.1 

—2.0 

+  0.3 

2  

-4.3 

—3.0 

—1.1 

—0.2 

-3.0 

—1.9 

—1.0 

—0.1 

+2.8 

4-2.6 

+0.1 

+  0.1 

-2.3 

—2.0 

—0.2 

3  

-4.5 

—3.2 

—1.0 

—0.3 

-3.1 

—2.3 

—0.7 

—0.1 

+  2.3 

+2.6 

+0.1 

-0.2 

—  2.9 

—1.8 

—0.6 

4  

-4.3 

—3.4 

—0.8 

—0.1 

-3.2 

—2.5 

—0.5 

—0.2 

+1.7 

+2.2 

-0.2 

-0.3 

—  3.7 

-1.5 

—0.6 

5  

-3.3 

—3.2 

—0.2 

40.1 

-2.8 

—2.9 

—0.1 

+0.2 

+1.3 

+1.6 

+0.2 

40.  1 

-4.5 

—0.5 

40.2 

6  

-2.2 

—2.9 

+0.5 

+  0.2 

-2.1 

-3.2 

+0.5 

+  0.6 

+  1.3 

+0.8 

+0.2 

+0.3 

—  5.3+1.2 

1.1 

7  

1.1' 

—2.3 

+0.9 

+0.2 

—1.2 

—2.8 

+1.1 

+0.5 

+  0.8 

+0.1 

+0.3 

40.4 

—  5.0+2.3 

+  1.1 

8  

-0.3 

—1.0 

+0.7 

0-0 

—0.6 

—2.1 

+1.5 

0.0 

+0.3 

-0.5 

0.  -1 

+0.4 

—  3.6 

+2.6 

10.  4 

9  

+0.2 

—0.7 

+  1.0 

-0.1 

—0.2 

—1.8 

+1.6 

0.0 

—0.4 

—1.3 

+0.5 

+0.4 

—  3.8 

+3.1+0.3 

10  

+0.5 

+0.1 

+0.6 

—0.2 

-0.3 

-1.2 

+1.0 

-0.1 

—1.4 

—1.9 

+0.4 

40.1 

—  3.0 

+2.0-0.2 

11  

+0.7 

+  1.0 

0.0 

-0.3 

-0.5 

—0.3 

—0.1 

—0.1 

—2.5 

—2.4 

+0.1 

—0.2 

—  1.7 

0.0-0.6 

12  

+1.2 

io 

-0.7 

—0.1 

—0.8 

it.  « 

—1.2 

—0.2 

-3.2 

-2.8 

-0.1 

—0.3 

—  0.2 

—2.0-0.6 

24.7 

23.4 

21.3 

MARCH. 


12  a.... 

+2.3 

+3.0 

—0.7 

0.0 

+0.1 

+0.9 

-0.7 

—0.1 

-2.  6:—  2.  8 

+0.4 

—0.2 

+  1.1 

—1.0 

-0.3 

1  

+2.7 

+3.3 

—0.8 

+0.2 

+0.3 

+  1.4—1.1 

0.0 

—2.6—3.0 

+0.3 

:  ii.  i 

+  1.7 

-1.6 

+0.3 

2  

+3.0 

+4.1 

-0.9 

-0.2 

+  0.6 

+1.8—1.2 

0.0 

-2.  7  -3.  1 

0.0+0.4 

+  2.8 

-2.1 

40.2 

3  

1-3.2 

+4.2 

—  0.  .s 

—0.2 

o.  :i 

+2.0 

—1.2 

40.  1 

-2.  6  -2.  8 

—0.3 

+0.-S 

+  3.4 

-2.3 

H  0.4 

4  

1-3.5 

+4.4 

—0.6 

-0.3 

|1.3 

+2.4 

—1.1 

0.0 

-2.4 

-2.5 

—0.3 

+0.4 

+  4.1 

—2.0 

+  0.1 

5  

+3.5 

+3.9 

—0.2 

-0.2 

+  1.  8 

+2.4 

—0.7 

+0.1 

-1.9 

—1.9 

—n.2 

+  0.2 

+  4.4 

—1.1 

+0.1 

6  

:i.  M 

+3.5 

+0.2 

0.0 

+2.4 

+2.2 

+0.1 

+0.1 

—1.6 

-1.2 

—0.2 

—0.1 

+  4.5 

H  o.i 

0.0 

7  

+3.1 

+2.3 

+0.7 

+0.1 

+2.9 

+  1.7 

l.ll 

+0.1 

-0.6 

-0.5 

4-0.2 

—0.3 

+  3.5 

+  1.9 

-0.1 

8  

•L  :; 

+1.5 

+0.8 

0.( 

:u 

+1.6 

1.6 

-0.1 

O.o 

+0.5 

0.0 

—0.2 

+  3.6 

+2.4 

-0.3 

9  

+1.8 

+0.8 

+  0.8 

+  0.2 

+2.7 

+0.9 

+  1.8 

0.0 

1-1.5 

+  1.0 

+0.4 

+0.1 

+  2.7 

+4.0 

+  0.3 

10  

-0.6 

—0.8 

+0.4 

—0.2 

+  1.6 

11.  :; 

+  1.3 

0.0 

+2,6 

4-1.6 

+0.6 

+  0.4 

+  1.1 

+2.3 

(0.2 

11  

-2.1 

—1.8 

-0.1 

—0.2 

1-0.4 

—0.3 

+0.6 

+0.1 

+3.3 

+2.3 

+0.  B 

+  0.5 

+  0.2 

+  1.0 

+0.4 

12  p.... 

-3.7 

—2.7 

-0.7 

—0.3 

—1.4 

—0.7 

-0.7 

0.0 

+3.4 

+2.6 

+0.4 

+0.4 

-0.8 

—1.0 

+0.1 

1  

-4.3 

—3.3 

-0.8 

—0.2 

-2.4 

-1.4 

—1.1 

+0.  1 

+3.  2 

+2.7 

+0.3 

+0.2 

-2.0 

—1.6 

+  0.1 

2  

—4.7 

—3.8 

—0.9 

0.0 

-3.0 

—1.9 

—1.2 

+0.1 

+2.7 

+2.8 

0.0 

—0.1 

-2.9 

—2.1 

0.0 

3  

-1.8 

—4.1 

—0.8 

+0.1 

:;.  :;     2.2 

—1.2 

+0.1 

+2.1 

+2.7 

—0.3 

—0.3 

-  3.  6  —2.  3 

-0.1 

4  

-t.7 

—4.1 

—0.6 

0.0 

-3.41-2.2 

—1.1 

—0.1 

1.7 

+2.2 

—0.3 

-0.2 

-  4.1 

—2.0 

-0.3 

5  

-3.9 

—3.9 

—0.2 

+0-2 

:;.  1     2.  4 

—0.7 

0.0 

1.5 

+1.6 

—0.2 

-1-0.  1 

-4.7 

—1.1 

+0.3 

6  

—2.9 

-2.5 

(1.2 

—0.2 

—2.  2  -  2.  3 

+0.1 

0.0 

1.2 

+1.0 

-0.2 

+  0.4 

-  3.8 

+0.1 

+0.2 

7  

—1.8 

-2.3 

+0.7 

—0.2 

-1.0—2.1 

+1.0 

+0.1 

0.  '.I 

+0.2 

40.2 

!  0.5 

-4.2 

+  1.9 

+  0.4 

8  

—0.7 

—1.2 

+0.8 

-0.3 

40.l!—  1.5 

+1.6 

0.0 

I).:; 

—0.1 

li.li 

+  0.4 

L-  2.8 

+2.4 

+0.1 

9  

o.  :: 

-0.3 

+0.8 

-0.2 

1  0.  8  —  1.  1 

+1.81+0.1 

-0.7 

—1.3 

0.4 

+0.2 

—  2.  7  +4,  0 

+0.1 

10  

+1.3 

+0.  9 

+0.4 

0.0 

-1  0.91-0.  5 

+1.3 

+0.1 

—1.5 

—2.0 

+0.6 

-0.  1 

—  1.6+2.3 

0.0 

11  

+1.9 

+1.9 

—0.1 

+0.1 

+0.7     0.0 

+0.6 

+0.1 

-2,3 

—2.5 

+0.5 

—0.3 

—  0.  6:+1.0 

-0.1 

12  

+2.3 

+3.0 

—0.7 

0.0 

+0.1 

+0.9 

—  0.  7  -0.  1 

-2.6 

—2.8 

+0.4 

-0.2 

+  1.1 

—1.0 

-0.3 

:«>.:: 

28.6 

26.3 

13 


important  differences  exist  between  these  two  sets  of  stations, 
the  plateau  computation  is  not  reproduced  in  this  paper.  The 
separation  of  the  wave  of  AB  into  components  was  accom- 
plished by  the  precepts, 

12a+12/J     la+lp 
semidiurnal  wave  =  11=      — „ '    — o — '  etc., 


tridiurnal  wave  =111  = 


12a+8a+4p     la+9a+5/> 


,  etc., 


3  3 

diurnal  =  I  =  J/?  —  (II  -f  HI)  at  each  hour. 

The  pressure'  J2?,  Table  1,  and  the  temperature  JT,  Table 
2,  were  each  computed  in  the  same  way.  AB  is  given  in  units 
TABLE  2.— Diurnal,  semidiurnal,  and  tridiurnal  temperature  wares— Cont'd. 

APRIL. 


£ 

195  meters. 

400  meters. 

1000  meters. 

Sums. 

AT. 

t 

n. 

III. 

AT. 

I. 

II. 

III. 

AT.      I.      IL      IIL 

< 

HI. 

1 

•-ai 

+4.  1 

+5.6 

-1.2 
—  1  4 

-as 

—  0.  1 

-  1   2 

-2.7 

-0.9 
-13 

-0.6 

—0.5 

1 
-1.9—1.7     0.0—0.2 
-1  5—1.7  -0.2     O.C 

.-..  2  —2.  1 
t  6.6—2.5 

—1.3 
—0.3 

2.  .    .. 

-1  6.  0—1.4 

0.  •_ 

+1.7 

-3.3—  1.5—  0.1 

-1.3—1.6  -0.1  -0.1 

-    7.7-- 

3  

-6.1 

-1.1 

—1.3    -II.'. 

-1.0—1.2-0.1  -0.3 

-  7.  7  —2.  5      1.4 

4  

-5.3 

-0.6 

1-2.6 

-~:.\ 

-0.6-0.9—0.1      0.4 

7.'.i—  1.0      1.0 

5  

5.  I 

-4.9 

-0.  3  —0.  1 

r2.7 

-2.  7  —0.  1 

-0.  1 

-0.4—0.5-41.2  -0.  :: 

J-  7.1      0.0-0.3 

6  

3.9 

-0.2 

^2.6 

- 

-  0.  2 

—0.2 

-0.1—0.2     0.0  -0.1 

+  6.3+1.0 

—0.3 

7  

:,2—  0.4 

r2,5 

-1.9    -1.1 

-0.5 

-0.4      0.3  -0.2—0.1 

4.7  -2.5 

—1.0 

l.i 

-1.2—a; 

- 

-2.0 

+ae-o.e 

•.  4  —  0.  2 

-1.3 

9  

-0.3—0.6 

-1.0 

-0.1 

-1.2 

+o.  iU0.s 

-1.5     0.9  -0.6     0.0 

-   l.fi      1.7 

—0.3 

10  

—1.7 

-2  2 

-0.3 

-0.2 

-0.3 

-0.6—  a  i 

;.  7     :.-_' 

-1.3  -1.3 

-0.2 

11..   .. 

-ae 

-::.  4  -0.  1 

-0.2 

—1.9 

-0.1  -o.; 

..3  -0.2  -0.3 

-  4.  0  -0.  1 

-1.4 

12  p 

-5.4-4.4—1.2 

0.2 

-2.4 

-1.9—0.9  -0.4 

-1.9-1.5     0.0-0.4 

-  4.  ^  —  2.  1 

-1.0 

1.      .. 
2..    .. 

-.4  -1.4—0.1 

—7.-,  —5.9—  1.4—  0.2 

-as 

-4.6 

-•2.6  -  ! 

.'.  —u.  2 

+  1.8  +1.3  -".  - 
-1.4  -1.2   -0.  1    -O.I 

J.  5      li.3 
-7.6—-    - 

3..    .. 

-7.4 

—5.9 

-1.1—0.4 

—5.0 

-3.2  -1.3—0.5 

+0.9  +1.1-0.1  —0.1 

-  S.  0  —  2,  5  —1.  0 

4  

-6.5 

—5.  4  -0.  i) 

-0.5 

-4.4 

—  i  9  —  a  9r—  0.  6 

0.  4    -  0.  7  —0.  1  —0.  2 

-  7.6-1.6—1.3 

5..    .. 

—1.  fi 

—  U 

-0.  3  —0.  1 

-2.9 

—2.  6  —0.  1  —ii.  2 

0.0  -0.2—0.2      0.0 

-  7.  2     0.  V—  0.  3 

6  

-±  fi  —  3.  6 

-0.8 

- 

-2.2 

-2.3 

-  0.  2  —0.  1 

—  0.  1      0.  0     0.  0  -0.  1 

—  5.9   -I.O      0.2 

7..    .. 

. 

l._ 

- 

—1.7 

: 

0.0-0.5  -0.2   HH1 

-4.5     2.5+1.4 

8  

- 

-1.2 

+0.9 

-O.l 

-0.6 

-0.4 

-0.1    -0.9  -0.4  -0.4 

-1.8  -2.2 

1.0 

9  

0.  7 

-l.ll—  0.  1 

-1.1 

-".  1 

+0.1 

-0.4—1  3  -0.6  -0.3 

-  0.  5  -I!  7 

+0.3 

10  

_ 

!  - 

-0.3—0.2 

-1.3 

-0.9 

+0.6 

—0.2 

-1.0—1.5   -0.4  -0.1 

-    l.il      1.1 

-0.3 

11..    .. 

-3.  6  —  0.  4  —0.  4 

+  1.0 

-1.4 

0.  i 

- 

-i..-,  -i.i;  -0.2—0.1 

-  3.4—0.1 

—1.0 

12..    .. 

-3.1 

+4.81—1.2—0.5 

+0.6 

2.1 

—0.9 

-0.6 

-1.  9  —1.  7     0.  0  —a  2 

+  5.2—2.1 

—1.3 

42.6 

40.6. 

36.91 

I 

MAY. 


12  a 
1. 

4.5  -5.3—0.6-0.2 
-4.6  -6.1—1.0—0.5 

. 
-0.7  -0.3—1.3   -0.3 

-0.8—0.7-0.2 
-0.  8  —0.  4  —0.  5 

-a, 

-0.1 

-  4.4—  1.S+O.I 
-  6.  0  -2.  8  —0.  1 

2. 

1.7      6.4-1.3'—  0.4 

-0.9-0.6—1.- 

—0.  8  —0.  1  —0.  8 

-0.1 

-  6.9—  as 

-0.1 

3. 

.4—1.3—0.3 

.1-1.8  —  0.  1 

—".-     0.3—1.0 

o.o 

-a* 

4 

J.  -      5.  9  —  1.  0  -0.  1 

.2—1.5—0.2 

-o.:;    0.8—1.0 

-ai 

-  7.9—  as 

-0.4 

5. 

-4.5-5.0—0.5      0.0 

-0.5  -   .4—0.7—0.2 

-o.  f.   -  1.1—0.5 

0.0 

-  7.5—1.7 

-0.2 

6. 

'.2      0.0 

-1.6  -   .3      0.4-0.1 

-1.4  -1.1  -0.2 

-0.1 

-  7.1  -0.8 

0.0 

7. 

-    -       -          ".7—  O.S 

.:;     1.3-0.2 

-2.2      1.4-0.7 

o.l 

-  5.0  -2.7 

+ai 

8. 

1.5    -0.7  -1.0—0.2 

-  a  6  -   .1    2.  i     u.  : 

-2.7   -1.5-1.1 

0.1 

t  3.5  +4.2 

+ai 

9. 

-0.5  -0.9  -0.9—0.5 

-3.3  -  .0   -2.0-0.3 

1.4  -1.2 

1.5  -4.1—0.1 

10. 

-2.5  -IS      0.  4—  4i.4 

17      1.5-0.2 

-2  1  -1.1      0.9  -0.  1 

-  o.  7  -2.  g|—  0.  1 

11. 

4  ^  %  \  —  fi  2  —  11.  ;J 

'.  7  —  0.  1 

-1.4      1.0  -0.4      0.0 

-  i.  ;»  -u.  :i 

-0.4 

12  P 

-5^  6  -i.  9  —  o!  6  —  a  1 

—0.5      0.2—' 

-0.  2 

-ai 

-  a9-i.s 

-a  4 

1. 

-6.6-5.5—1.0      0.0 

-1.8-0.3  -1.3—0.2 

-0.  1    -n.4—0.5 

O.C 

-  5.  5  -2.  S 

-a2 

2. 

-7.2-5.9-1.3      0.  (1 

-2.5—  0.7—  1.7-0.1 

-      •  .1—  0.  8  -0.1 

-  6.  7  —3.  8 

0.0 

3. 

7.3—5.8-1.3—0.2 

-2.*—1.->—}    - 

-1.2-0.3-1.0 

-0.1 

-  7.  3  —4.  1 

-0.1 

4 

-6.7—5.5—1.0—0.2 

-2.5—  .2—1.5  -0.2 

-1.  7-<i.  s  -1." 

-0.1 

-  7.  s  -a  s  +a  i 

5 

5.5  —  L.I—  0.5   -ii.  .- 

.  4  —  0.  7  -0.  3 

-l.i;—  1.2—  0.5 

-0.1 

-  7.  1  —  1 

6. 

-a  5  —3.  3  -0.  2—0.  4 

—  0.  !'  —  .  .->      0.  4  -0.  2 

-1.1-1.4-'    - 

-  6.  2  - 

7. 

-1.5  -1.9  -0.7  -0.3 

-0.2—  .4      1.3—0.1 

-1.5  -0.7 

0.0 

-  4.  8      - 

8. 

-0.5  -1.4  -1.0—0.1 

-  0.  5  -   .4    -2.  1  —0.  2 

-0.5—1.5  -1.1 

—0.1 

-  4.  3  -4.  2  —0.  4 

9. 

2.2    -1.3  -0.9      0.0 

-0.6-  .2  -2.0—0.2 

—0.4  —1.6  -  1.2   ao 

-  1.5  -4.11—0.2 

10. 

3.  2  -3.  6  -0.  4      0.  0 

-0.5  -0.9   -1.5—0.1 

—0.4—1.4  -0.9 

-0.1 

-  1.  3  -  . 

11. 

3.9  -4.3—0.2—0.2 

-0.  5  — 

-0.6—1.1  -0.4 

U.I 

12. 

4.  5  -5.  3  -0.  6  -0.  2 
54.5 

-0.  5  —  0.  2  —0.  5  -0.  2 

-0.  s  —  0.  7  —  0.  2 
47.2! 

0.1 

-   4.  4  -  : 

of  0.001  inch  of  mercury;  JTis  in  units  of  one  degree  Fahr- 
enheit; the  height  is  in  meters,  as  in  the  Blue  Hill  mixed 
system  of  units.  In  order  to  make  the  temperature  curves 
directly  comparable  with  the  pressure  curves  on  the  diagrams, 
the  sign  of  the  J  T  was  reversed  in  the  beginning,  so  that  the 
entire  temperature  computation  should  have  opposite  signs  to 
give  the  natural  actual  values.  The  mean  daily  value  of  the 
temperature  T  is  given  for  each  month  under  the  column  J  T, 
so  that  by  reversing  the  signs  of  JT  and  adding  to  T  the 
actual  hourly  temperatures  which  were  used  maybe  recovered. 
The  component  curves  of  AB,  I,  II,  III  are  to  be  found  at 
the  top  of  the  sections  of  figs.  26-37,  one  for  each  month  of 

TABLE  2. — Diurnal,  semidiurnal,  and  tridiurnal  temperature  warts — Cont'd. 

JULY. 


S 

195  Meters. 

400  Meters. 

1000  Meters. 

Sums. 

1 

AT.     I.       0.     III. 

AT.      I.   |   H.     m. 

AT.;  L|IL   m. 

i.    |  u.    in. 

12  a   .. 

^a  8  +5.  2  -L  2  -0.2 

-0.2  -0.8—0.4—0.2 

0.0+0.3—0.1—0.5 

+  6.3-1.7-0.6 

1..  .. 

4.  .j     5.  9  —  1.  4     0.  0 

+1.2+1.5-0.2—0.1 

rO.  8  +0.  8  -0.  1  —0.  1 

-  8.2—1.5—0.2 

2..  .. 

-5.0-6.3—1.3     O.C 

-2.1-2.1     0.0     O.C 

+1.  6  -1.5  -0.2—0.  ; 

f  9.9—1.1  -0.1 

3..   .. 

-5.2-6.5-1.2     O.C 

-2.9  -2.6  -0.2  -0.1 

T2.3  -2.3  -0.1—0.1 

-11.4  -as    o.o 

4.  .  .. 

-5.3-6.2-0.7—0.2 

-a  s  -a  i-o.  2    o.o 

-2.8  -2.5  -0.2  -0.1 

n.^-as-ai 

5..  .. 

-5.0-5.3—0.1—0.  ! 

-3.3-3.0  -0.2  -0.1 

+  2.8+2  7—0.1  +il 

i-ll.O     0.0  -,0.1 

6..  .. 

-4.4      4.4-0.6-0.6 

-3.1  +2.9  +  ai  -0.1 

-2.6  -2.  7  —  0.  2  -rO.  1 

r  10.  0-0.  5—  a  4 

7..  .. 

-35  -2.5  -1.3—  0.3 

-2.8  -2.6  -0.1  -0.  J 

-2.1  -2.6-0.2     O.I 

7.7    -  1.2-0.2 

8..  .. 

2.4  -1.2+1.4—0.2 

-2.1  -2.4—0.1—0.2 

^1.8  -2.2—0.2     0.1 

r  5.8  +  1.1—0.6 

9..   .. 

+0.  7—  0.5+1.2     O.I 

+  1.5  -1.5  -0.1—  ttl 

-1.6  -1.5  -0.1  —0.1 

-  2.5  -1.4—0.2 

10  .   ... 

-L8—  1.6—  0.2     0.0 

-0.  7  -0.  6  JO.  1      a  C 

+0.8-rl.O  —  0.  1      0.  ' 

0.0—0.2—0.1 

11   .   ... 

4.  1  -  3.  6  —0.  5     0.  ( 

0.0—0.1     0.0-0.1 

+a2+0.4—  0.1  -ai 

-  a  s  —a  6    o.  o 

I2p  ... 

—  6.  2  —  4.  8  —  1.  2  —  0.  2 

—  1.  0  -0.  6  -0.  4     a  < 

-as  -0.2-0.  i  -o. 

-  5.6—1.7—0.1 

-7.  2  -5.  6  —  1.  4  —0.  2 

-1.5—1.4—0.2  -0.  J 

-0.7—1.0-0.1  -0.1 

-  8.0—1.5-0.1 

2'!   '.'.' 

—7.6—5.7—1.3  —  0.6 

-2.1—2.2     0.0-0.1 

-1.4—1.7  -0.2  -0. 

-  9.6—1.1—0.4 

3  .   ... 

—7.5  -6.0—1.2—0.3 

-2.6—2.9-0.2-0.1 

—2.  1  —2.  2  -0.  1     0.  ( 

-11.1  —0.9  -a? 

4  .    .. 

-6.7—5  8—  0.7—  0.2 

-2.9—2.9-0.2-0.2 

-2.4—2.4  +0.2-0.: 

-IL  1—0.3     0.6 

5  .   ... 

5^  2  —  5  1  0.  1     0.  ( 

—3.0—3.1  -"-0.2—  0.1 

-2.9-2.7-0.1-0.] 

-10.9     O.O-fl.2 

6  

-a2-a8^o!e    o.o 

-2.9—  a  0-0.1     O.C 

-2.  9  —2.  6  —0.  2  —0.  1 

-  9.4+0.5  -0.1 

7  .   .. 

—  1.0—  2.3-1.  S     O.C 

-2.7—  2.9-ai  +ai 

-2.8—2.5-0.2-0.- 

-7.7+1.2     0.0 

8  

-0.4-0.8-1.4-O.S 

-2.  2  -2.  1  -0.  1      0.  C 

-2.2—2.1—0.2  -0.1 

-  5.  0T1,1—  0.  1 

9  .   .. 

-1.7   -0.7  -1.2-  0.2 

-1.4—1.6-0.1  -0.1 

-1.5—1.8  -0.1  -0.1 

1.4+ttl 

10..   .. 

-  1.5  -2.3—0.2-0.6 

-0.6-0.8  +0.1  +0.1 

-0.  9  —0.  9  —0.  1  -rO.  1 

r  0.6—  0.2—  tt4 

11..   .. 

-3.1  -3.9—  0.5-^U 

0.  0  —0.  1     0.  0  +0.  1 

-0.3-0.4-0.1     O.c 

-  a4—  0.6—  O.2 

12..   .. 

i.2-1.2-0.2 

+0.2-0.8-0.4-0.2 

0.  0  -0.  3  -0.  1  —0.  : 

+  6.3—  LI—  ae 

66.  gj 

66.0 

59.8 

AUGUST. 


12  a.    .. 
1. 

-a  2  -5.  o-i.  3  -as 

4.4     5.5—1.0—0.1 

+0.  5  +1.5J—  0.5-0.5 
-rO.9-2.4—  1.1—  0.3 

-0.6+0.4-0.7'—  as 

-0.2  -1.0—0.7—0.1 

r  6.5-2.5-1.3 

+  a9—  2.8—  as 

2. 

4.9-5.7—0.8     tt( 

-1.5-2.6—1.2   -0.1 

-1.1  ^1.6-0.6 

-0.1 

+  9.9—  2.6-i-a2 

3 

-5.1 

-5.  7—0.  7  -  0.  1 

^2.  2  -2.  3  —0.  .'.      0.  4 

-  1.9      2.0 

-0.3 

-0.2 

+10.0—1.5+0.7 

4.       .. 

5.2 

-5.5—  a  4 

+a  i 

-2.5      2.5—0.5   -0.5 

—0.2 

-0.2 

+  10.2-1.1  -O.S 

5.       .. 

-4.6 

-4.  3  -0.  3 

ao 

2.7  -2.4  -0.1   -0.2 

-2.4  -2.1 

-0.2 

-'-a  i 

+  8.8  -0.6  +0.3 

6.        .. 

-as  -ai  -o.s—  0.1 

2.5  -2.0  -0.6  —  ai 

-2.  4  —2.  2 

-0.3—0.1 

-7.3  -1.7—0.3 

7.       .. 

•14 

-i.s  -a  9  -as 

2.2  -1.3  -1.0—0.1 

-2.3  -1.9 

+0.  6  —0.  2 

-   5.  0  -  2.  5  —0.  6 

8.       .. 

-1.2 

-0.7  -i.o—  as 

1.5  -i.o  -i.o—  as 

-2.2  -1.8 

-0.7—  a  a 

r  3.5-2.7-1.3 

9. 

-a  8,—  i.  2  -o.  s  —o.  i 

-1.0  -0.3   -1.0—  0.3 

-1.7 

-0.6—0.1 

+  0.3-2.1—4X5 

10.       .. 

-2.  6  -2.  5  —0.  1 

O.C 

0.0—0.6  -0.5  -0.1 

-0.9 

-0.5 

-0.3-0.1 

-  2.6+0.7-0.2 

11. 

—1.2 

-0.1 

—0.7—1.2  -0.1  -a  4 

0.0 

0.0 

-0.2 

-0.2 

-4.9-0.7  -0.7 

12p.    .. 

-5.8 

-4.6-1.3 

-0.1 

-1.5—  2.  5—  0.5  -O.S 

-a? 

—0.3 

—0.7 

-0.2 

-7.4-2.5   -O.S 

1 

-6.3—5.3—1.0 

O.l 

-3.  0  —  i  1  —1.  1  -0.  i: 

-1.6 

—1.0—0.7 

-0.1 

-  8.4-2.  S  -0.3 

2.       .. 

-6.5-5.6—  as,—  a  i 

-3.8-2.5—1.2-0.1 

-2.2 

—1.5—0.6—0. 

-  9.6—  2.6—  as 

3.       .. 

—5.  4  —0.  7 

-s.  2  -2.  6  -as—  a  i 

-2.5 

—2.0—0.3—0.2 

-10.0—1.5  -0.6 

4. 

5.8 

-4.9-' 

-3.  5  —2.  5  —  0.  5  —0.  5 

—2.6 

—2.1  -0.2-0.3 

—  9.5—1.1—1.3 

5.       .. 

—4.0—1.2-0.3—0.1 

—2.5-2.3  +ai--C.3 

-2.1 

0.2 

—0.1 

'.6—0.5 

6 

-2.2  -3.0-0.8-0.0 

-1.3—2.0  -0.6  -0.1 

—1.8 

—2.3 

-0.3 

-0.1 

-7.3   -1.7+a2 

7.       .. 

-0.6—1.6  -0.9 

-0.1 

1 

-1.2 

—2.0 

-0.6 

-0.2 

-  5.  2  -  2.  5  -0.  7 

8.      .. 

-as 

—0.3  -1.0 

-a  i 

0.5—1.0  -1.0  -0.5 

-0.8 

—  1.  7 

-0.7 

-0.2 

—  3.0-2.7  -0.8 

9.       .. 
10.       .. 

2.4 

-1.3-0.5 
-2.6—  ttl 

ao 

—0.1 

-0.9—0.3  -1.0-0.2 
-  0.9  -0.5      0.5,—  0.1 

-0.5 
-0.4 

—1.2      0.6  -0.1 
—  0.  6  -0.  3  —0.  1 

.      J.  1-0.3 
-  2.5  -0.7-0.3 

11.      .. 

ao 

-a  9  —o.  6 

—0.3 

-O.S  -O.S  -0.1—0.1 

-0.3 

-0.  1  —a  2  —0.  2 

-  4.8—0.7-0.6 

12.       .. 

3.2 

-5.0—1.3 

-O.S 

+a5+L5—  0.5-0.8 

-0.6 

+0.  4—0.  7 

-as 

+  6.9i—  2.5—  1.3 

65.2 

I 

64.5! 

57.? 

1 

JUNE. 


SEPTEMBER. 


12  a   ... 

-4.2    -5.5 

-0.6 

—0.7 

- 

-o.  a-o.  e 

1.4 

-1.1 

+a  si—  o.  2 

-    ".2 

—  1.  5      12  a. 

2.  5     3.  7  —1.  2J    0.  0 

-0.6 

I 
-0.5—  1.0,  —0.1 

-0.7  -as—  a  7—  o.s 

4.  -.—2.9—  a  4 

1  

-4.  '."   -5.7 

—0.5 

-0.3 

- 

—0.8 

—0.5 

-1.7 

'.2      0.0 

-10.4 

—  i!i 

—as      i...    . 

+3.0  -4.5—  1.3—  as 

-1.0 

-0.3 

—1.3     0.( 

-0.7  -0.3—  0.9—  a  1 

+  5.  1  —3.  5  —0.  3 

2  

-5.3  -6.7 

—1.3—0.1 

-2.3 

—1.1 

-0.1 

-2  -0.1 

12.  4—  2.6 

—  0.  1        2.  .  .     . 

a4    4.7-1.1  —  aa 

-1.1 

-a  5  -1.5  -ai 

-0.6+0.6—1.2     O.C 

r  5.8—  as—  0.4 

3  

-5.5  -fi.  8—1.3 

0.0 

-2.6 

2  4 

-2.4—0.4      ".4 

-12.8—3.0 

+0.7        S...     . 

-!.  --0.9 

—0.5 

-0.9 

0.3—  1.3,  +0.1 

—0.4  -  0.7—1.1      0.  ( 

-  5.  8  —a  3  -0.  1 

4  

-5.3   -1x4—1.2 

-0.1 

-2.7 

-1.3  -0.4 

2.4 

-  2.  4  —0.  5  -  0.  5 

-12.  5—3.  0 

—  1.0         4.  .. 

;.3—  0.  4 

-0.1 

-0.4 

-0.6 

-0.9—0.1 

-0.3  -O.S  -0.7  -0.2 

-  5.7—2.0     0.0 

5  

•-.  2i—  0.  5 

".  'J 

-3.9 

-1.3 

-0.; 

2.4 

.  3   -  0.  a 

-11.3 

—2.1 

-i-a9      5!!!    '. 

-4.  0  -  :: 

O.C 

+0.2 

^0.3—0.2  -0.1 

-1.0     0.  f     0.0  +0.2 

!.  1    -0.3 

6  

-3.9    -: 

—0.4 

2.7 

-2.7 

+0.1 

-0.1 

-2,3 

2.1 

a  o;  +o.  2 

- 

-0.3        6.-..     . 

-3.7 

-0.1 

+0.8 

+0.1 

-0.  6  -0.  1 

-1.3     O.S  -0.5     0.( 

!.6  -0.2 

7  

'1.5 

-0.6 

. 

L8 

+  1.0 

—  0.3 

-2.0 

1,6 

M.  4      u.  ' 

-  6.3  -1.9 

—0.9        7...     . 

3.  0 

0.0 

+  1.4 

0.0 

1.:-.     0.  1 

-1.5  T-1.0  -0.6—0.1 

+  2.8+ai      0.0 

8  

-1.3  -1.2    -0.  S—  0.  ; 

-1.7 

-1.1 

+L2 

—  0  ( 

-1.4 

1.2 

-0.4—0.2 

T  3.5 

.  ; 

—1.5        8... 

2.  1      0.  7  -1.4 

ac 

1.6 

-0.1 

+  1.6—0.1 

-1.5  -0.6  -1.2—0.3 

-   1.4  '4.2—0.4 

9  

-0.  1  —0.  4 

-0.8-0.3 

-0.9 

1.1 

-0.  5 

1.2 

0.4  -0.  >      0.' 

J-  1.3 

-2.7—0.8         9...      . 

0.0  -0.6  -O.S—  0.2 

-1.6 

0.0 

-1.6      0.0 

-1.3      0.4      1.0—0.1 

-  0.2  -as—  o.s 

10  

-1.  -  -2.  1 

-0.  4  —0.  1 

O.Oj-0.7 

0.  6  —II.  1   -  0.  6  -0.  1 

-  2.  9 

-l.>—  0.  1       10...      . 

-2.21—1.9     0.0-0.3 

-0.2 

-1.2-0.1 

+a»+a2    0.6    o.o 

11  

-a  7  —3.  s 

-0.1 

O.C 

-1.1-1.7 

-a  2—  0.  B  -0.4      0.4 

-  6.1 

-      0.7       11... 

-3.7 

-2.9-0.6 

-0.2 

0.  1  -0.  2 

•  o.  4  -  a  i 

.1      0.0 

-  a  o-o.  5-0.  i 

12  i<  ... 

-5.  3  -4.  8  -0.  6 

-0.1 

. 

-0.4 

-0.4 

—1.4   -0.5—0.5 

+  1.0      12  p.      . 

-4.9 

^-a&—  1.2 

O.C 

—  .4—  0.3-1.  0-ai 

-a  6  —  o.  i  —  o.  7    o.  i 

—  4.  0  —2.  9      0.  0 

1..    ... 

-5.  8  -5.  5 

-0.5 

-0.2 

—3.5      .'.'.' 

-O.S 

^0.2 

-1.4 

-2.1    -0.2  -0.5 

-10.5 

-1.1 

+0.9         1...     . 

-5.  5 

-4.2—1.3      0.0] 

-  .6—0.4 

-1.3  -0.1 

-1.  1  -0.  4  —0.  9  -0.  2 

-  5.  0  —a  5  -  0.  3 

2  

7   -  -6.1 

-1.  3  —0.  4 

—  4.5!-3.  3 

-1.1-0.1 

-2.  4  —2.  4  —0.  2  J-0.  2 

-      1 

—0.3        2...      . 

-5.  5 

-4.5  -1.  ' 

+a  i 

-  .  S  —0.  4  —1  .5  -  0.  1 

-1.7—  US—  1.2      0.0 

-  5.4-:    - 

3  

-8.1-6.2-1,3 

-0.6 

-5.  2  —3.  6 

•    3 

-0.3 

-3.1 

-17  -'1.4      0.  ti 

-IX.  5 

-ao 

—0.9        3  ..     . 

—5.4 

-4.5—0.9      0.0 

-  .7—0.5—1.3      0.  ] 

-l.S-0.  fi—  1.1   -0.1 

-  5.  fi  —  : 

4  

-7.6—5.7 

1.2 

' 

-5.3      a  4  -1.3 

-O.H 

-2.8 

-0.  5  —0.  2 

-10.9—3.0 

1—1.5        4...      . 

i.2—  0.  4     0.0 

—  .4-0.4—  0.9—  0.  1 

-1.  7  —0.  7  —0.  7  —0.  3 

-  5.  3  —2.  0  -0.  4 

5  

-5,8—5.0 

—0.3 

-4.3  -2.5-1.3 

—0.5 

—3.  0  —2.  7  —0.  3     0.  0 

-10.2 

—2.1 

—0.8        5  ..      . 

-3.  5—  a  6  -0.3—0.2 

-0.6-0.4—0.2      O.l 

-1.0—0.9      0.0—0.1 

-  4.9      0.1—0.3 

6  

'-;.  s  -o.  i  —o.  i 

-2.  5  -2.-->  -n.  1 

-0.1 

-2,3 

—2.  4      0.  0  -  0.  1 

-  8.7 

+a2 

-0.1         6...     . 

-2.  1  -2.7   -0.8—0.3 

-0.4—0.1 

-  0.  6  —0.  1 

—  O.R—  0.8-0.5     O.t 

-3.6  -1.6—0.4 

7  

-1.8—2.3 

-0.5 

O.C 

- 

-1.3—2.1  -0.4+0.4 

-6.2 

-1.9 

+0.7         7  .. 

-0.7 

-1.7  -1.2-a2 

-1.2—0.2 

1.3  -0.1 

-0.3—0.3-0.6     O.C 

-  2.2   -a  1—0.1 

8  

-0.2—0.7 

ii  - 

0.1 

-11.7      0.1      1.2      0.4 

-0.6 

—1.5 

-0.  4  -  0.  5 

—  3.1 

-'.4      1.0         8...      . 

—0.6  -1.4—0.1 

-  1.  6  -0.  1 

+  1.6—0.1 

0.8)—  a  «    -  i 

-  1.1      4.2      0.0 

9  

1.5  -0.5 

0.2 

-1.3      II.  0   -1.  1 

-0.2 

-0.4—0.9 

- 

-0.4 

+0.9        9...      . 

1.5 

-0.7  -  ' 

-  1.6—  a  I 

1.1;    o.  i 

0.7—11.5      1. 

*•  o.i    a  4    as 

10  

2.  fi  -2.1 

-0.4 

-1.5   -0.»+0.8 

-0.1 

-ai 

-0.6  -0.2 

+  as 

-1.8 

-0.3       10...     . 

2.2 

-2.1      i' 

-1.4  -0.1 

-1.2  -0.1 

-0.3—0.3-0.6      O.C 

-  1.9     ; 

11  

3.5     3.0  -0.1 

-0.6 

-1.7      1.7      0.3 

-a; 

1.2      0.  S 

0.  4      0.  0 

+  5.5'  +0.8 

—  ag     11... 

2.4 

-a  o  —o.  6    o.  o 

+  0.6  -0.1 

-  a  4  -  o.  i 

—  It  i  n  ;i      it  1  —  0  1 

5      ii.O 

12  

4.2  -5.5—0.6 

-0.  7 

1.7      2.6-0.3 

-9.6 

1.4 

M 

+a5-0.2 

+  9.2—0.4 

-1.5       12  

3.7—1.2 

0.0 

-0.6  -as 

—  1.  0  —0.  1 

-o.7+a3-o.7-o;s 

-  4.5—2.9—0.4 

62.2 

60.7 

54.4 

58.5 

57.6 

51.3 

14 


the  year.     The  following  characteristics  of  these  waves  may 
be  noted. 

Diurnal  wave. — In  January  the  amplitude,  av  is  about  0.011 
inch,  and  this  increases  to  0.018  in  August,  which  seems  to  be 
the  maximum.  The  phase  of  the  maximum  in  January  is  at 
6—7  a.  m.,  and  that  of  the  minimum  is  at  6-7  in  the  evening. 
The  morning  maximum  phase  is,  apparently,  about  one  hour 
later,  7-8  a.  m.  in  the  summer,  and  the  evening  minimum 
phase  is,  also,  one  hour  later,  7-8  p.  m.  Thus,  there  is  a 
slight  advance  of  one  hour  in  the  times  of  maximum  and  min- 
imum in  passing  from  the  cold  season,  with  the  sun  in  the 

TABLE  2. — Diurnal,  semidiurnal,  andtridiurnal  temperature  waves — Cont'd. 

OCTOBER. 


i4 

I 
a 

195  meters. 

400  meters. 

1000  meters. 

Sums. 

AT. 

I. 

II. 

III. 

AT. 

I. 

II. 

III. 

AT. 

I. 

II. 

III. 

L 

II. 

III. 

12  a.      . 

+  1.6 

+3.0 

—1.2 

—0.2 

—1.3 

-0.5 

—0.8 

0.0 

-2,1 

—1.5 

-0.8 

+0.2 

+  1.0 

-2.8 

0.0 

1. 

+2-3 

+3.7—1.2 

—0.2 

-1.6 

—0.6 

—1.2 

+0.2 

-2.  1  —1.  5 

-0.9+0.3 

+  1.6 

—3.3 

+0.3 

2. 

i<> 

+3.  8  —0.  9 

—0.0 

—1.9 

—0.7 

—  4.4 

+0.2 

—2.  0  —1.  4 

—0.8:  +0.2 

+  1.7 

—3.1 

+  0.4 

3. 

+3.4 

+4.  0  |  0.  6 

0.0 

-1.8 

—0.7 

—1.2 

+0.1 

—1.7—1.2 

—0.61+0.1 

+  2.1 

—2.4 

+0.2 

4. 

+3.6 

+3.4 

+0.1 

+0.1 

—2.1 

—0.7 

—1.2 

—0.2 

—0.9—1.0 

0.0+0.1 

+  1.7 

—1.1 

0.0 

6. 

+3.5 

+2.9 

+0.6 

0.0 

-0.6 

—0.6 

-0.1 

+  0.1 

0.  0  —0.  8 

+0.61+0.2 

+  1.5 

+  1.2 

+0.1 

6. 

+2.9 

+2.  1  +0.  9 

—0.1 

+0.3 

—0.4 

+0.7 

0.0 

+0.  6  -0.  3 

+0.  9     0.  0 

+  1.4 

+2.5 

—0.1 

7. 

+2.2 

+  1.5+1.0 

-0.3 

+1.0 

—0.3 

+  1.4 

—0.1 

+  1.2+0.1 

+  1.1     0.0 

+  1.3 

+3.5 

—0.4 

8. 

+1.1 

+0.4 

+0.9 

—0.2 

+  1.7 

0.0 

+1.7 

0.0 

+  1.7,  +0.3 

+  1.2  +0.2 

+  0.7 

+3.8 

0.0 

9. 

-0.4 

—0.6 

+0.4 

-0.2 

+  1.7 

—0.1 

+  1.6 

+0.2 

+  1.8;  +0.5 

+  1.01+0.3 

-0.2 

+3.0 

+0.3 

10. 

-1.6 

—1.5 

—0.1 

0.0 

+1.3 

+0.2+0.9 

+0.2 

+1.5 

+  1.0 

+0.3 

+0.2 

-0.3 

+1.1 

+0.4 

11. 

-3.  '2 

—2.4 

—0.8 

0.0 

+0.5 

+0.  6—0.  2 

+0.1 

+1.0 

+  1.3 

—0.4 

+0.1 

-0.5 

—1.4 

+0.2 

12  p      . 

-4.0 

—  2.9 

—1.2 

+0.1 

—0.3 

+0.  7j—  0.  8 

—0.2 

+0.5 

+1.2 

—0.8 

+0.1 

-1.0 

—2.8 

0.0 

1 

-4.6 

—3.3 

—1.3 

0.0 

-0.7 

+0.  4  —1.  2 

+0.1 

+0.4 

+1.1 

—0.9 

+0.2 

-1.8 

—3.3 

+0.1 

2. 

-4.6 

—3.6 

-0.9 

—0.1 

-0.8 

+0.6 

-1.4 

0.0 

+0.4 

+1.2 

—0.8 

0.0 

-  1.8 

—3.1 

—0.1 

3. 

-4.4 

-3.6 

—  0.  6—0.  2 

-0.  6  +0.  7 

-1.2 

-0.1 

+0.5 

+1.1 

-0.6 

0.0 

-1.8 

—2.4 

-0.4 

4. 

—3.4 

-3.3 

+0.1—0.2 

-0.3+0.9—1.2 

0.0 

+0.9 

+0.7 

0.0 

+0.2 

-1.7 

—1.1 

0.0 

5. 

-2.4 

-2.8 

+0.  6  —0.  2 

+0.5+0.41—0.1 

+0.2 

+1.1 

+0.2 

+0.6 

+0.3 

-2.2 

+1.21+0.3 

6. 

-1.2 

-2.2 

+0.9 

+0.1 

+  1.1  +0.2 

+0.7 

+0.2 

+1.1 

0.0 

1).  !) 

+0.2 

-2.0 

+2.5 

+0.4 

7. 
8. 

-0.2 

+0.6 

-1.2 
-0.4 

+  1.0 
+0.9 

0.0 
+0.1 

+1.7+0.2 
+1.  7  +0.  2 

+  1.4 
+  1.7 

+0.1 
-0.2 

+  0.9 

+0.7 

-0.3 
—0.6 

+1.1 
+  1.2 

+0.1 
+0.1 

-1.3 

-0.8 

+3.5 
+3.8 

+0.2 
0.0 

9. 

+1.1 

+0.7 

+0.4 

0.0 

+1.5—0.2+1.6 

+0.1 

+0.1 

—1.1 

+  1.0 

+0.2 

-0.6 

+3.0 

+0.1 

10 

+  1.4 

+1.6 

—  0.  1  —0.  1 

+  0.5—0.4+0.9 

0.0 

—0.9 

—1.2 

+0.3 

0.0 

0.0 

+1.1 

—0.1 

11. 

+1.6 

+2.7 

—  0.  8  —  0.  3 

-0.  8  —0.  5 

—0.2 

—0.1 

-1.8 

—1.4 

-A  4 

0.0 

+  0.8 

—1.4 

—0.4 

12. 

1-1.6 

+3.0 

—1.2 

—0.2 

-1.3 

—0.5 

-0.8 

0.0 

-2.1 

—1.5 

-0.8 

+0.2 

+  1.0 

—2.8 

0.0 

i<;.  6 

46.7 

40.1 

NOVEMBER. 


12  a 

+2.0 

--2.8 

—1.1 

+0.3 

-1.0 

—1.1 

—0.5 

+O.G 

-0.1 

—0.1 

-0.4+0.4 

+  1.6 

-2.0 

+1.3 

1. 

--2.  1 

••3.4 

—1.5 

+0.2 

—1.6 

—1.2 

—0.8 

+0.4 

-0.2 

—0.1 

-0.5-4-0.4 

--  2.  1 

-2.8 

+1.0 

2. 

--2.2 

•-3.6 

—1.4 

0.0 

-1.9 

—1.1 

-0.8 

^0.0 

-0.4 

0.0 

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--2.5 

—2.7 

+0.1 

3. 

--2.4 

•-3.9 

—1.2 

—0.3 

-2.0 

—1.0 

-0.7 

—0.3 

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--2.8 

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^0.7 

4. 

--2.8 

--3.3 

-0.4 

—0.1 

-2.0 

—0.8 

—0.5 

-0.7 

-0.7 

0.0 

-0.  3  -0.  4 

--2.5 

-1.2 

—1.2 

5. 

+3.0 

--3.6 

-0.1 

—0.5 

-0.9 

-0.6 

+0.1 

-0,4 

-1.2 

—0.1 

-0.5-0.6 

--2.9 

—0.5 

—1.5 

6 

+3.2 

•-2.9 

--0.  5 

-0.2 

--0.7 

—  0.  2  +0.  8 

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0.0 

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-  -  2.  7 

+1.6 

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7. 

4-3.5 

•-2.2 

--1.2 

+0.1 

--1.5 

0.0+1.1 

+0.4 

+0.8 

0.0 

4-0.  6+0.  2 

--2.2 

+2.9 

8. 

4-3.0 

•-1.2 

+1.5 

+0.3 

--1.8 

--0.  3 

+0.9 

+0.6 

+1.2 

0.  0  +0.  8|+0.  4 

--  1.5 

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9. 

4-1.8 

•-0.4 

--1.2 

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•-1.7 

--0.6 

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+0.4 

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0.0 

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--  1.0 

+2!  5 

4-i.o 

10. 

—0.1 

-0.7 

--0.  6 

0.0 

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-  -0.9 

+0.1 

0.0 

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4-o.i 

--  0.4 

+0.9 

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11. 

—2.3 

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-0.4 

—0.3 

--0.5 

-  -1.1 

—0.3 

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0.0 

+0.1 

0.0 

—0.1 

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-o!? 

12  p 

-4.2 

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—1.1 

-0.1 

0.0 

--1.2 

—0.5 

-0.7 

—0.7 

4-0.1 

—0.4 

—0.4 

-1.7 

—2.0 

—1.2 

1. 

—5.0 

-3.0 

—1.5 

—0.5 

--0.  1 

--1.3 

-0.8 

—0.4 

-0.7 

+0.4 

—0.5 

-0.fi 

—  1.3 

—2.8 

—1.5 

2. 

—5.0 

—3.4 

-1.4 

-0.2 

•  41.3 

--1.0 

—0.8 

+0.  1 

-0.5 

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—0.5 

0.0 

—  2.4 

-2.7 

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3. 

—4.8 

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--0.  9 

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0.0 

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-2.8 

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4. 

—4.0 

—3.9 

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•  -1.0 

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-2.9 

—1.2 

4-1.3 

6.       . 

—3.2 

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6. 

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-2.7 

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—  2.7 

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8. 

0.0 

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0.0 

—0.2 

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4-0.8 

—0.4 

—  1.7 

4-3.2 

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+0.6 

—0.1 

--1.2 

—0.5 

-0.4 

-0.7 

--0.  7 

—0.4 

--0.2 

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—  0.  6  4-2.  5 

—1.5 

10. 

4-1.2 

+0.8 

--0.6 

-0.2 

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—1.0 

+0.1 

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--0.  1 

-0.1 

4-0  2 

0.0 

—  0.3 

+0.9 

—0.1 

11. 

+1.6 

45.9 

-0.4 

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-1.0 

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4-2.0 

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—1.1 

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—0.5 

+0.6 

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—0.1 

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+6.4 

£  1.6 

—2.0 

+1.3 

:tn.  (I 

40.1) 

34.3 

DECEMBER. 


12  a 

4-1.2 

--1.8 

-0.8 

+0.2 

—1.7 

-2.4 

+0.2 

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--2.4 

0.0 

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1. 

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2. 

•-1.5 

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3. 

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0.  C 

+  3.3 

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4 

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--3.5 

—  0.  9  —0.  3 

5. 

--3.0 

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0.0 

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7. 

•-3.2 

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0.0 

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--3.  1 

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10 

•-1.1 

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4-0.9 

4-0.2 

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0.0 

4-1.0 

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11. 

—1.3 

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—2.2 

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0.0 

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12  p 

—2.8 

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-3.8 

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+0.3 

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2.0 

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7. 

—1.0 

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0.0 

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9. 

+0.2 

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—  1.0 

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12. 

BLJ 

28.2 

+1.1 
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-0.8 

0.0 
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—1.8—2.3 

—1.7—2.4 
30.0 

•4).  2 
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+0.3 
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23.4 

•  -2.4 
4-2.4 

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I  1.2 

4-1.8 

—0.2 
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—0.1 
+0.4 

Southern  Hemisphere,  to  the  warm  season,  with  the  sun  in  the 
Northern  Hemisphere. 

Semidiurnal  wave. — The  two  maxima  occur  with  remarkable 
steadiness  at  about  10  a.  m.  and  10  p.  m.  throughout  the 
year,  though  they  are  a  little  later  in  the  summer  than  in  the 
winter.  The  minima  occur  at  3-4  a.  m.  and  3-4  p.  m.  in  the 
winter,  and  about  one  hour  later  4-5  a.  m.  and  4-5  p.  in.  in 
the  summer.  The  ascending  branch  of  the  curve  is,  there- 
fore, a  little  less  inclined  than  the  descending  branch  during 
the  winter,  but  in  summer  they  are  quite  symmetrical.  The 
amplitude  of  the  curve  is  about  0.018  in  January  and  some- 
what less  in  the  summer,  0.014  in  June,  0.015  in  July. 

Tridiurnal  wave. — There  is  much  more  fluctuation  in  this 
minor  wave  than  in  the  two  others  just  described.  In  Decem- 
ber, January,  and  February  the  amplitude  is  about  0.006,  with 
maxima  at  2  a.  m.,  10  a.  m.,  6  p.  m.,  and  minima  at  6  a.  m.,  2 
p.  m.,  10  p.  m.  On  the  other  hand,  in  the  summer  the  ampli- 
tude is  about  one-third  as  great,  0.002,  but  the  phase  is  reversed 
so  that  the  maxima  occur  at  7  a.  m.,  3  p.  m.,  11  p.m.,  with  the 
minima  at  3  a.  m.,  11  a.  m.,  7  p.  m.  The  change  of  phase  ap- 
pears to  take  place  between  March-April,  August-September, 
so  that  the  larger  amplitude  is  developed  while  the  sun  is  in 
the  Southern  Hemisphere,  and  the  smaller  while  it  is  in  the 
northern,  the  transition  taking  place  at  the  equinoxes  as  the 
sun  crosses  the  equator.  This  is  the  third  instance  in  which 
an  inversion  phenomena  has  been  detected  in  the  earth's  at- 
mosphere, due  the  orbital  solar  action:  (1)  The  inversion 
of  the  magnetic  and  meteorological  elements  as  described  in 
my  Bulletin  No.  21;  (2)  the  inversion  or  surging  of  the  at- 
mosphere as  to  its  temperature  between  the  Tropics  and  the 
temperate  zones,  and  as  to  its  pressure  between  the  Eastern 
and  the  Western  hemispheres,  as  shown  in  the  MONTHLY  ' 
WEATHEB  REVIEW,  November  1903;  and  (3)  in  the  tridiurnal 
pressure  wave  as  exhibited  in  this  paper.  Whatever  may  be 
the  causes  of  these  phenomena  of  inversion  it  is  evident  that 
the  mere  interference  of  waves  of  different  periods  can  not  be 
the  sole  cause.  The  subject  will  require  careful  and  exhaust- 
ive investigation  of  the  numerous  forces  operating  in  the  com- 
plex circulations  of  the  solar  and  terrestrial  atmospheres. 

THE  DIURNAL,  SEMIDIURNAL,  AND    TRIDIURNAL  TEMPERATURE  WAVES 
IN  THE  LOWER  STRATA  OF  THE  ATMOSPHERE. 

An  inspection  of  the  temperature  curves  given  in  the  pre- 
ceding paper,  MONTHLY  WEATHER  REVIEW,  February,  1905,  makes 
it  evident  that  the  temperature  waves  in  the  successive  strata 
of  the  lower  atmosphere  differ  very  much  from  the  wave  observed 
at  the  surface.  We  may  suppose  that  the  pressure  waves  are 
closely  connected  with  the  temperature  variations  in  the  lower 
strata,  and  that  the  changes  in  the  density  produced  by  the 
variations  in  temperature  become  converted  into  pressure 
changes  in  part  by  thermodynamic  processes.  The  subject  is, 
of  course,  complex,  and  its  final  solution  will  require  more  de- 
tailed examination  than  it  has  been  possible  to  make  at  this 
time.  I  have  decided  to  execute  a  rough  sort  of  integration 
of  the  en  tire  temperature  effect,  by  computing  the  components 
for  the  curves  deduced  on  the  planes  at  195,  400,  and  1000 
meters  elevation.  The  agreement  between  this  result  and  the 
actual  one  existing  in  the  atmosphere  from  the  surface  to  3400 
meters  can  be  only  approximate,  but  the  outcome  serves  to 
indicate  that  the  temperature  waves  in  the  free  air  are  the  di- 
rect cause  of  the  pressure  waves  as  a  density  rather  than  as  a 
dynamic  effect.  The  temperatures  on  these  three  planes  were 
scaled  from  the  diagrams,  each  one  was  separated  into  its  I, 
II,  III  components,  and  then  the  sums  for  each  type  on  these 
three  planes  were  computed.  The  details  of  this  work  are 
given  in  Table  2,  since  they  are  of  general  interest,  and  the 
second  section  of  the  diagrams  under  each  month  in  figs.  26—37 
gives  the  corresponding  temperature  curves.  I  repeat  the 
statement,  that  for  convenient  comparison  of  the  temperature 


15 


waves  with  the  pressure  waves  the  numerical  signs  have  been 
reversed  throughout  the  temperature  computation. 

Diurnal  waw. — These  temperature  waves  have  been  con- 
structed without  using  the  surface  temperatures,  and  this  im- 
plies that  the  temperatures  in  the  several  strata  are  chiefly 
concerned  in  generating  the  pressure  waves  that  are  observed 
at  the  respective  elevations.  Of  course  some  additional  influ- 
ence must  be  expected  to  work  in  from  the  adjacent  strata 
not  here  reckoned  in  the  integration,  and  therefore  the  results 
here  discussed  do  not  exhaust  the  entire  scope  of  the  avail- 
able sources  of  inquiry.  A  close  approximation  to  a  parallel- 
ism between  the  pressure  and  the  temperature  systems  is 
certainly  indicated.  In  January,  February,  and  March  the 
diurnal  curves  of  temperature  and  pressure  are  in  close  agree- 
ment as  to  amplitude  and  phase,  and  reversing  the  sign  of  A  T, 
we  obtain  the  relation, 

-  4°  JT  oc   +  0.010  AB,  or  —  1°  F  +  oc  0.0025  inch. 
With  the  approach   to  summer  the  curve  of  temperature  in- 
creases in  amplitude  more  rapidly  than  the   pressure  curve, 
and  the  phase  of  maximum  and  of  minimum  in  July  and  August 
is  about  three    or  four  hours    earlier,  4  a.  m.  for   tempera- 
ture and   7  a.  m.  for  pressure,  or  3:30  p.  m.  for  temperature 
and   7:30  p.  m.  for  pressure.     The  semidiurnal   temperature 
waves  are,  however,  smaller  than  would  be  expected  and  pos- 
sibly I  have  not  obtained  exactly  the   correct  temperature 
curves  to  resolve  into  components  in  these  two  months.     We 
have  an  approximate  relation, 

-  12°  AT  oc   +  0.017  AB,  or  -  1°  F  oc   +  0.0014  inch. 

It  follows  that  in  summer  the  influence  of  one  degree  of  tem- 
perature to  change  the  pressure  is  about  one-half  as  much  as 
it  is  in  the  winter.  This  implies  a  series  of  complex  functions 
which  it  is  not  possible  to  discuss  in  this  place. 

Semidiurnal  wave. — The  most  important  fact  brought  out  by 
this  computation  is  that  a  true  semidiurnal  wave  of  tempera- 
ture is  developed  in  the  lowe?  strata  whose  phase  for  the  maxi- 
mum ordinate  persists  steadily  throughout  the  year  at  8  a.  m. 
and  8  p.  m.,  with  the  minimum  at  2  a.  m.  and  2  p.  m.,  except 
that  in  summer  the  minimum  occurs  about  one  hour  earlier. 
Generally  the  temperature  maxima  precede  the  pressure  maxi- 
ma by  about  two  hours,  implying  that  the  semidiurnal  pres- 
sure wave  follows  the  temperature  wave  at  an  interval  of  two 
hours  throughout  the  year.  In  winter  the  amplitudes  have 
nearly  the  following  relation, 


—  3°  AT  x   +  0.018  AB,  or  —  1°  F  oc    +  0.0030  inch, 
while  in  summer  the  relation  is  follows, 

-2°JToc    +  0.015  AB,  or  —  1°  F  a:    +  0.0075  inch. 

Hence,  the  temperature  wave  in  summer  is  two  and  one-half 
times  as  effective  in  producing  the  pressure  wave  as  it  is  in 
the  winter.  In  considering  the  dynamic  relations  of  these 
waves,  it  is  necessary  to  bear  in  mind  that  the  entire  system 
is  moving  from  east  to  west  in  the  atmosphere,  or  from  right 
to  left  in  the  diagram,  and  the  relative  position  in  the  semi- 
diurnal, as  in  the  diurnal  waves,  is  that  the  temperature  waves 
precede  the  pressure  waves.  If  a  physical  process  is  con- 
cerned, as  the  vertical  movement  of  convectional  currents  with 
expanding  heads,  or  the  downward  flow  of  cool  air  along  the 
sides  of  the  warm  diurnal  cone,  then  this  time-lag  of  two 
hours  represents  the  interval  connecting  the  temperature  cause 
with  the  pressure  effect.  It  is,  however,  quite  clear  that  the 
diurnal  pressure  waves  have  their  origin  in  a  temperature 
wave,  rather  than  in  a  forced  dynamic  wave  as  suggested  by 
Lord  Kelvin. 

Tridiurnal  ivave. — We  shall  divide  the  year  into  two  portions 
for  discussing  the  tridiurnal  wave:  first,  October  to  March, 
and,  second,  April  to  September.  In  the  winter  period  it  is 
seen  that  a  fair  agreement  exists  in  the  phases  of  the  maxima 
of  the  temperature  and  the  pressure  waves,  and  that,  with  the 
system  of  coordinates  here  employed,  they  are  in  approxi- 
mately direct  synchronism.  In  the  summer  months,  on  the 
other  hand,  although  the  correspondence  between  the  two 
sets  of  curves  is  much  less  satisfactory,  there  is  suggested  a 
synchronism  of  the  inverse  type,  such  that  the  phases  of  the 
temperature  and  pressure  are  opposite  to  one  another.  It  will 
hardly  be  safe  to  lay  down  more  definite  conclusions  regarding 
these  tridiurnal  curves,  because  we  should  not  only  require  to 
have  for  discussion  very  perfect  original  curves  in  the  atmos- 
phere, but  also  it  would  be  necessary  to  integrate  throughout 
the  entire  range  in  altitude — that  is,  through  the  strata  of  the 
atmosphere  affected  by  the  diurnal  disturbance — instead  of 
limiting  our  summation  to  three  selected  curves. 

A  further  discussion  of  these  curves  in  connection  with  the 
vapor  tension,  the  electric  potential  gradient,  the  coefficient 
of  dissipation,  and  the  phenomena  of  atmospheric  electricity 
generally  will  be  found  in  the  next  paper  of  this  series,  while 
their  relations  to  the  diurnal  variation  of  the  earth's  magnetic 
field  will  be  taken  up  in  a  still  later  paper. 


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HI.— THE  DIURNAL  PERIODS  OF  THE  VAPOR  TENSION,  THE  ELECTRIC  POTENTIAL,  AND  COEFFICIENT  OF  DISSIPATION. 


THE  DIUBNAL  VARIATION  OF  THE  VAPOE  TEXSIOX. 

In  the  Monthly  Weather  Review  for  December,  1902, 1  made 
some  remarks  upon  the  phenomena  involved  in  the  changes  of 
the  semidiurnal  periods  of  the  barometric  pressure,  the  at- 
mospheric electric  potential-fall,  and  the  vapor  tension,  as  they 
occur  at  the  surface  of  the  earth,  into  the  simple  diurnal 
periods  which  are  observed  in  the  strata  above  the  ground. 
The  present  series  of  papers  properly  supplements  that  paper, 
but  in  this  connection  attention  is  fixed  upon  the  annual  va- 
riations in  these  two  related  periodicities  for  the  purpose  of 
determining  the  exact  physical  processes  operating  to  produce 
the  transformations  recorded  in  those  periods.  Especially  it 
is  proposed  to  lead  up  to  an  explanation  of  the  diurnal  periods 
in  the  earth's  magnetic  field,  which  seem  to  be  simply  a 
meteorological  effect  of  the  radiation  of  the  sun  in  the  lower 
strata  of  the  atmosphere,  through  the  intermediate  develop- 
ment of  currents  of  electric  ions  in  connection  with  the  pre- 
vailing distribution  of  the  temperature. 

The  hourly  values  of  the  vapor  tension  at  the  surface  were 
not  available  at  the  Blue  Hill  Valley  Station,  and  I  decided 
not  to  take  Boston,  preferring  a  more  inland  station  which 
should  be  freer  from  seacoast  influences.  In  consequence  of 
the  convenience  of  the  published  record  at  Pare  St.  Maur, 
Paris,  the  mean  diurnal  variations  of  vapor  tension  at  that 
place  for  the  five  years,  1897-1901,  were  computed,  the  results 
being  given  in  Table  3.  These  variations  at  each  hour  rela- 
tive to  the  daily  mean  are  transferred  to  the  curves  of  figs. 
38—49,  being  the  lower  curve  of  each  month.  In  order  to  ob- 
tain the  hourly  values  of  the  vapor  tension  in  the  free  air  for 
the  levels  195,  450,  and  1000  meters  at  Blue  Hill,  I  proceeded 
as  follows:  The  temperatures  computed  at  these  elevations 
in  Fahrenheit  degrees  were  read  from  figs.  14-25,  and  they 
may  be  recovered  from  Table  2,  by  reversing  the  sign  of  J  T 
as  there  recorded.  These  temperatures. were  converted  into 
degrees  centigrade.  With  this  as  an  argument  the  vapor 
tension  E  was  taken  from  Table  43  in  the  Smithsonian  Meteor- 
ological Tables,  edition  of  1896,  for  saturation.  Then,  with 
the  observed  relative  humidity  at  these  levels  for  each  hour, 
the  corresponding  vapor  tension,  e  =  E  x  R.  H.,  was  com- 
puted, and  the  results  are  given  in  Tables  4,  5,  and  6.  These 
variations  of  the  vapor  tension  above  the  surface  are  also 
transferred  to  figs.  38-49,  the  mean  monthly  values  appearing 
on  the  zero  line,  and  the  ordinate  divisions  being  0.40  mm.  The 
values  of  the  relative  humidity  in  the  free  air  at  Blue  Hill  were 
extracted  from  the  same  report,  and  for  each  month,  at  the 
levels  195,  400,  1000  meters,  all  the  available  data  were  col- 
lected. Certain  interpolations  were  made  from  observations 


at  other  heights,  when  practicable,  in  order  to  obtain  more  ma- 
terial for  this  discussion.  The  means  were  taken  at  each  hour, 
and  plotted  on  diagrams,  and  average  lines  were  drawn 
through  the  points,  from  which  approximate  values  were 
found.  Then  these  values  of  the  relative  humidity  for  the 
hours  12  a.  in.,  4  a.  m.,  8  a.  m.,  12  p.  m.,  4  p.  m.,  8  p.  m.,  were 
placed  on  a  second  system  of  sheets  with  the  months  as  one 
argument,  and  mean  lines  were  drawn.  From  these  curves, 
which  smoothed  out  minor  irregularities,  the  second  approxi- 
mate hourly  values  at  six  points  were  found,  and  transferred 
to  the  first  system  of  curves,  which  were  reconstructed  by 
the  aid  of  them.  This  method  of  double  cross-plotting  involv- 
ing two  approximations,  as  before  stated,  is  capable  of  dealing 
successfully  with  very  rough  data.  An  examination  of  the  set 
of  curves  in  the  figs.  38-^9  "Diurnal  variation  of  the  vapor 
tension,  Je,  in  the  four  levels  50  meters,  Pare  St.  Maur,  Paris, 
195  meters,  Blue  Hill  summit,  400  and  1000  meters  in  the  free 
air  over  Blue  Hill,"  leads  to  the  following  remarks  on  the  be- 
haviour of  this  element  in  the  lower  atmosphere. 

(1)  The  mean  vapor  tension  for  the  day  decreases  from  a 
maximum  at  all  levels  in  July  and  August  to  a  minimum  in 
the  same  levels  in  February,  and  from  a  maximum  at  the  sur- 
face in  each  month  to  a  series  of  lower  values  with  the  increase 
in  elevation.     This  course  is  parallel  with  the  seasonal  change 
in  the  temperature,  as  may  be  seen  by  comparing  the  series  of 
curves  in  figs.  14-25.     The  vapor  content  of  the  atmosphere 
is  strictly  a  function  of  the  temperature  and  the  sources  of 
evaporation  of  aqueous  vapor,  but  for  any  given  locality  it  is 
a  function  of  the  temperature  alone  when  general  averages 
are  considered. 

(2)  For  the  diurnal  period   at  the  surface  the  year  divides 
into   two   portions:    first,  November   to  February,  when   the 
diurnal  variation  has  a  single  maximum,  about  3  p.  m.,  and  a 
single   minimum,  about   6   a.  m. ;    second,  March  to  October, 
when  the  semidiurnal  period  is  developed  with  maxima  about 
8  a.  m.,  8  p.  m.,  and  minima  at  4  a.  m.  and  3  p.  m.,  approxi- 
mately.    In  March  the  maxima  are  located  more  closely  to- 
gether, also  in  October,  than  in  the  other  months,  showing 
that  there  is  in  this  connection  a  transition  between  the  single 
diurnal  and  the  semidiurnal  periodic  systems.     By  comparing 
these  curves  with  the  series  of  figs.  2-13,  "  Temperature-falls 
in  the  lower  strata,"  it  is  seen  that  the  fully  developed  maxima 
of  the  vapor  tension  occur  exactly  in  the  midst  of  the  hours 
of  the  most  rapid  temperature  changes,  8  a.  m.,  8  p.  m.     When 
the  lower  atmosphere  is  heating  most  rapidly  from  the  sur- 
face upward,  convection  currents  form,  which  rise  in  the  fore- 
noon, carrying  the  products  of  fresh  evaporation  with  them 
as  an  increase  in  the  vapor  tension.     The  surfaces  covered 

19 


with  dew  and  moisture  deposited  during  the  night  ai'e  in  a 
favorable  condition  for  rapid  evaporation.  The  first  heat  of 
radiation  on  the  ground  acts  primarily  on  the  vegetation  and 
fills  the  air  with  vapor  as  fast  as  the  process  of  evaporation 
can  proceed.  The  midday  minimum  occurs  at  the  time  of 
greatest  effective  temperature,  but  it  is  a  minimum  for  the 
vapor  tension  because  the  supply  of  moisture  for  evaporation 
is  not  sufficient  to  keep  the  same  degree  of  relative  humidity 
at  the  higher  temperature  then  prevailing.  The  vapor  con- 
tents that  rise  in  the  first  wave  are  carried  aloft  to  about  2000 
meters,  or  the  height  of  the  diurnal  temperature  effect,  and 
there  is  not  sufficient  aqueous  vapor  at  the  surface  to  fill  the 
air  undergoing  this  rapid  temperature  change  up  to  an  equal 
relative  humidity.  The  second  maximum  at  the  surface  is 
due  to  a  reverse  process  of  cooling,  which  begins  at  the  ground 
and  occurs  most  rapidly  at  8  p.  m.,  as  is  seen  from  figs.  2-13. 
The  convection  currents  at  that  hour  are  directed  earthward 
and  bring  the  aqueous  vapor  back  to  strata  which  are  lower- 
ing their  temperature,  and,  therefore,  develop  a  higher  rela- 
tive humidity.  This  cooling  action  extends  upward  slowly, 
with  a  considerable  time  lag,  until  it  gradually  dies  out  within 
a  few  hundred  meters  of  the  ground.  The  single  maximum 
of  the  upper  strata  seems  to  be  the  continuance  of  the  fore- 
noon maximum  in  the  lower  strata,  and,  except  for  June,  July, 
and  August,  the  afternoon  second  maximum  does  not  develop 
higher  than  400  meters.  The  entire  system  groups  itself  about 
the  curves  of  the  temperature-fall  in  a  very  harmonious  man- 
ner. The  vapor  rises  along  the  ascending  slope  of  the  tem- 
perature variation  and  falls  again  on  the  descending  slope. 
This  is  seen  clearly  in  the  summer  months,  where  the  time  of 
the  sun's  radiation  covers  the  hours  from  5  a.  m.  to  7  p.  m. 
In  the  winter  these  hours  are  much  contracted,  and,  the  tem- 
perature being  relatively  low,  the  vapor  tension  has  much  less 
chance  to  produce  the  double  maximum,  since  the  true  ver- 
tical convection  currents  are  comparatively  feeble. 

(3)  In  the  winter  there  is  a  marked  inversion  of  the  vapor 
tension  in  the  stratum  195  meters,  the  summit  of  Blue  Hill,  as 
referred  to  that  at  the  ground  50  meters,  or  at  higher  eleva- 
tions 400,  1000  meters,  such  that  a  minimum  occurs  during  the 
middle  of  the  day  and  a  maximum  at  night.  This  appears  in 
December,  January,  February,  March,  and  April;  in  the  other 
months,  the  rising  forenoon  maximum  reverses  it  back  again. 
Whether  this  is  a  characteristic  of  the  free  air  at  this  level,  or 
is  a  peculiarity  of  Blue  Hill  summit,  it  is  not  easy  to  deter- 
mine. It  may  be  noted  that  while  the  mean  vapor  "tension  de- 
creases with  the  height,  the  amplitude  increases  at  the  given 
elevations.  The  lower  temperature  of  the  higher  strata  causes 
the  vapor  tension  to  be  more  sensitive  to  masses  intruding 
from  below.  The  same  amount  of  aqueous  vapor  will  cause  a 
greater  change  in  the  tension  at  low  temperatures  than  at 
high,  and  hence  the  vapor  contents  rising  from  the  ground 
causes  greater  amplitudes  in  the  variation  of  the  hourly  values 
in  proportion  to  the  height.  Thus,  in  July  a  temperature  of 
65°,  with  range  from  56°  to  78°,  is  accompanied  by  a  change 
in  the  vapor  tension  Je=  0.70  mm.  at  the  ground,  while  at 
1000  meters  the  mean  temperature  of  60°,  with  range  from  57° 
to  62°,  is  attended  by  a  variation  Je=3.50  mm.  There  are 
numerous  other  circumstances  which  can  be  deduced  from 
these  diagrams,  such  as  the  gradients  at  each  hour  in  the  clay 
between  the  different  levels;  the  function  of  the  vapor  tension's 
relative  to  the  temperatures  in  the  free  air;  the  effect  of  the 
surface  in  disturbing  free  air  conditions,  which  it  would  be 
beyond  the  purpose  of  these  papers  to  discuss  at  this  time. 

THE    DIURNAL  VARIATION  OF  THE  ELECTRIC    POTENTIAL  GRADIENTS. 

The  three  series  of  observations  of  the  hourly  values  of  the 
atmospheric  electric  potential  gradient,  that  is,  the  fall  in  volts 

d  V 

per  meter,  —  —,  which  have  been  examined  in  this  connec- 
dn 


tion  are  those  at  Perpiguan1,  Paris2,  and  Greenwich3  for  the 
five  years,  1896-1900,  inclusive.  For  Perpignan  and  Paris  the 
curves  given  in  fig.  50  were  copied  from  the  diagrams  con- 
tained in  the  works  referred  to  above ;  while  for  Greenwich 
the  data  for  the  clear  and  rainy  days  combined,  as  well  as  for 
the  clear  days  by  themselves,  were  extracted  from  the  annual 
reports,  Tables  7,  8 ;  the  results  appear  for  each  month  in  fig.  5 1 ; 
the  clear  and  rainy  days  are  printed  in  dotted  and  the  clear  days 
alone  in  black  lines.  No  attention  has  been  paid  to  the  absolute 
values  in  volts,  as  it  is  proposed  simply  to  discuss  the  causes  of 
the  maxima  and  the  minima,  rather  than  the  amplitudes  of  the 
curves.  The  figs.  50,  51  show  that  a  maximum  occurs  dur- 
ing the  forenoon  hours,  7  to  11  a.  m.,  and  a  second  maximum 
is  found  in  the  evening  hours  from  6  to  11  p.  m.  The  Perpig- 
nan and  the  Paris  curves  suggest  that  the  morning  maximum 
occurs  earlier  by  about  two  hours  in  summer  than  in  winter, 
while  the  evening,  maximum  is  more  steadily  centered  at  7  to 
8  p.  m.  The  Greenwich  curves,  on  the  other  hand,  indicate 
that  there  are  really  two  maxima  in  the  forenoon,  and  two 
maxima  in  ihe  evening,  though  there  is  a  tendency  to  suppress 
the  first  morning  maximum  at  8  a.  m.  in  the  winter,  which 
gives  this  maximum  the  appearance  of  entering  earlier  in  sum- 
mer than  in  winter  as  on  the  French  curves.  The  evening  double 
maximum  seems  to  show  that  the  10-11  p.  m.  crest  is  steadier 
than  the  7-8  p.  m.  crest  throughout  the  year.  We  have  there- 
fore to  give  an  account  of  the  variable  8  a.  m.  and  8  p.  m. 
crests,  and  the  comparatively  steady  11  a.  m.  and  11  p.  m. 
crests. 

Before  proceeding  with  this  exposition,  I  will  further  intro- 
duce some  curves  of  the  daily  variation  of  the  rate  of  dissi- 
pation of  the  electric  charge,  q  =  — ~,  as  given  by  Zolss4,  and 

by  Gockel5,  in  the  Physikalisches  Zeitschrift.  They  appear  in 
fig.  52  for  Kremmiinster  in  the  winter,  and  for  Freiburg  in  the 
summer  and  the  winter.  While  the  observations  are  not  suffi- 
cient in  number  to  settle  definitely  the  normal  maxima  and 
minima,  yet  they  appear  to  indicate  two  crests  in  the  forenoon, 
8  a.  m.  and  10-11  a.  m.,  and  two  in  the  evening,  8  p.  m.  and 
10-11  p.  m.,  with  a  fifth  crest  about  3  p.  m.,  as  is  the  case  with 
the  atmospheric  electric  potential. 

There  is  yet  another  fact  which  can  be  brought  out  by  com- 
paring the  annual  numbers  of  the  atmospheric  electric  poten- 
tial at  Greenwich  with  the  well  known  variation  of  the  annual 
prominence  numbers,  as  given  by  me  in  the  Monthly  Weather 
Review  for  November,  1903.  The  Greenwich  numbers  are 
taken  from  the  annual  reports  of  that  observatory,  and  are 
to  be  found  in  Table  9,  "Variation  of  the  atmospheric  electric 
potential  numbers  on  an  arbitrary  scale ".  For  the  years 
1881-1888  the  scale  seems  to  be  different  from  that  of  the  years 
1890-1901  in  about  the  ratio  of  1  to  2,  and  I  have  multiplied 
the  first  set  by  the  factor  2  to  give  about  the  same  amplitude 
for  the  entire  series,  because  the  location  of  the  crests  will  not 
be  altered.  There  are  three  columns,  for  "All  days",  "Rainy 
days",  and  "Clear  days",  respectively.  These  data  are  plotted 
in  fig.  53,  "Annual  variation  of  the  number  of  solar  prominen- 
ces and  the  atmospheric  electric  potential,"  but  the  potential 
curves  are  plotted  in  an  inverse  sense  to  that  of  the  promi- 
nences. This  implies  that  an  increase  in  the  solar  activity, 
which  produces  the  prominences,  at  the  same  time  operates  to 
reduce  the  normal  atmospheric  electric  potential  near  the  sur- 
face of  the  earth.  The  number  and  the  location  of  the  crests 


1  Des  Variations  de  1'Electricite  atmospherique  a  Perpignan,  par  le 
Docteur  Fines,  1890,  Comptes  Rendus, 

1  Etude  de  la  variation  diurne  de  1'Electricite  atmospherique,  Par  M. 
A.-B.  Chauveau,  1902,  Bureau  Central,  Paris. 

3  Greenwich  Magnetlcal  and  Meteorological  Observations. 

«Phys.  Zeit.  5,  No.  10,  p.  259. 

5  Potentialgefalle  und  elektrische  Zerstreuung  in  der  Atmosphare.  A. 
Gockel,  Phys.  Zeit.  4,  No.  30,  pp.  871-876;  and  5,  No.  10,  pp.  257-259. 


21 


make  this  inference  probable  for  these  two  elements.  We  have 
already  shown  in  various  places,  summarized  in  the  same  paper, 
Monthly  Weather  Review,  November,  1903,  that  the  force  of 
the  deflecting  magnetic  vector  »•  has  a  variation  in  its  annual 
numbers  which  is  in  synchronism  with  that  of  the  prominence 
curve.  Hence,  the  magnetic  field  varies  directly,  while  the 
electrostatic  field  varies  inversely,  to  that  of  the  solar  energy, 
as  shown  by  the  frequency  of  the  prominences,  faculas,  spots, 
coronas,  and  the  intensity  of  the  radiation  generally. 

I  have  brought  together  the  several  typical  curves,  such  as 
emerge  from  an  inspection  of  the  charts  and  the  figures  of  the 
preceding  data,  in  fig.  54,  Section  I,  "Comparison  of  the  di- 
urnal periods  of  temperature-fall,  pressure,  temperature,  vapor 
tension,  electric  potential,  and  coefficient  of  dissipation".  They 
are  to  be  regarded  as  normal  types  of  periodicity  such  as  occur 
generally  most  vigorously  duriug  the  summer  months.  The 
temperature-fall  curve  is  from  figs.  2-13,  as  for  July;  the  semi- 
diurnal pressure  and  temperature  curves  are  from  figs.  26-37, 
with  some  little  change  in  the  amplitudes;  the  vapor  tension 
curves  are  from  figs.  38-49,  and  are  those  for  the  50,  195,  and 
400-meter  levels  in  the  midsummer;  the  electric  potential  gra- 
dient is  from  fig.  51,  and  the  coefficient  of  dissipation  is  from 
fig.  52.  It  should  be  remembered  that  the  relative  values  of 
the  ordinates  vary  as  follows: 

An  increase  of  the  ordinate  upward  means — 

(1)  A  greater  temperature-fall,  or  lowering  of  temperature. 

(2)  An  increase  in  the  pressure. 

(3)  A  decrease  in  the  temperature. 

(4)  An  increase  in  the  vapor  tension. 

(5)  An  increase  in  the  electric  potential. 

(6)  An  increase  in  the  coefficient  of  dissipation. 

From  fig.  54,  Section  II,  we  learn  that  the  double  crests  of 
the  electric  potential  and  coefficient  of  dissipation  belong  one 
to  the  temperature-falls  at  8  a.  m.  and  8  p.  m.,  and  the  other 
to  the  pressure-rises  at  10-11  a.  m.  and  10-11  p.  m.,  while  the 
3  p.  m.  crest  seems  to  be  associated  with  the  reversal  of  these 
curves  at  the  time  of  the  two  minima  in  the  afternoon.  The 
8  a.  m.  and  8  p.  m.  temperature  maxima  occur  in  the  midst  of 
the  most  rapid  temperature-rise  iu  the  forenoon,  and  the  most 
rapid  teniperature-fall  in  the  afternoon.  The  semidiurnal 
pressure  curve  lags  about  two  hours  behind  the  temperature 
effect,  and  it  must  be  closely  associated  with  the  dynamic  effect 
of  rapidly  rising  and  falling  vertical  convection  currents.  The 
exact  process  involved  in  this  retardation  is  worth  a  special 
investigation.  The  vapor  tension  curve,  also  due  to  tempera- 
ture action  in  producing  vertical  convection  currents,  lags  yet 
farther  behind  the  temperature  cause,  the  retardation  increas- 
ing from  three  hours  at  the  surface  to  four  or  five  hours  at 
higher  levels.  It  is  pointed  out  that  this  physical  convection 
in  time  between  the  vertical  and  horizontal  coordinates  affords 
a  means  of  computing  the  vertical  velocity  of  the  heads  of  the 
effective  waves  of  the  several  kinds.  One  must,  however,  take 
careful  note  of  the  circumstance  that  the  entire  system  is  be- 
ing propagated  from  right  to  left  on  the  diagram  with  a  veloc- 
ity proportional  to  the  linear  velocity  of  the  earth's  rotation 
at  the  latitude  of  the  station.  The  night  effect  is  overtaken 
by  the  advancing  cone  of  the  day  temperature  waves,  and  this 
makes  the  vertical  retardation  fall  to  the  right  in  ascending 
from  the  base  line  of  the  abscissas. 

From  these  considerations  it  is  evident  that  we  are  dealing 
with  a  temperature  effect  throughout  this  series  of  phenomena, 
and  that  it  is  confined  to  the  lower  strata  of  the  atmosphere, 
within  two  miles  of  the  surface,  because  the  diurnal  variation 
of  temperature  is  not  efficient  above  that  level.  Hence,  we 
must  conclude  that  they  are  all  consequences  of  the  solar  radi- 
ation, which,  as  is  generally  admitted,  is  the  cause  of  the  vari- 
ation of  the  diurnal  temperature  by  indirect  action  from  the 
ground. 

I  have  been  thus  careful  to  explain  that  we  are  concerned 


simply  with  the  lower  strata  of  the  atmosphere,  and  have  noth- 
ing to  do  with  the  higher  strata,  because  in  the  following  paper 
I  shall  be  able  to  show  that  the  diurnal  variation  of  the  mag- 
netic field  is  also  a  temperature  effect  in  the  lower  strata  of 
the  atmosphere.  We  may  now  make  some  further  remarks  on 
the  physical  cause  of  the  atmospheric  electricity  of  the  earth's 
gaseous  envelope. 

THE  CAUSE  OF  THE  ELECTRICITY  EX  THE  EARTH'S  ATMOSPHERE. 

A  brief  account  of  some  of  the  relations  between  the  ioniza- 
tion  and  electric  potential  of  the  atmosphere  can  be  found  in 
the  4th  -chapter  of  my  report  on  "Eclipse  Meteorology" 
Weather  Bureau,  Bulletin  I,  1902;  see  also  the  report  by  5l. 
A.  B.  Chauveau,  already  referred  to,  and  several  papers  by  H." 
Ebert,  Elster  and  Geitel,  P.  Lenard,  C.  Barus,-  and  others, 
containing  the  views  which  have  been  advanced  recently  to 
account  for  this  elusive  phenomenon.  It  is  conceded  that 
+  ions  and  —  ions  are  normal  constituents  of  the  atmosphere, 
and  that  their  generation  and  recombination,  with  the  attend- 
ant motions  of  their  electric  charges,  form  the  basis  of  this 
physical  process.  These  ions  are  produced  in  very  many  ways 
in  the  temporary  disintegration  of  the  dynamic  structures  of 
the  molecules  and  atoms,  by  which  they  are  temporarily  de- 
tached and  move  about  in  search  of  new  places  of  neutraliza- 
tion. The  most  prolific  source  of  their  formation  is  probably 
the  action  of  the  short  waves  of  the  solar  radiation  upon  the 
aqueous  vapor  of  the  atmosphere,  whether  visibly  condensed 
or  in  the  invisible  state.  There  is,  also,  a  further  source  of 
the  ions  in  the  action  of  the  electromagnetic  field  of  the  sun 
operating  upon  the  electric  and  the  magnetic  fields  of  the 
earth  within  the  gaseous  materials  of  the  atmosphere.  The 
complexity  of  the  physical  process  is  very  great,  and  I  shall 
confine  my  attention  more  to  the  modes  of  redistribution  of 
the  ions  found  in  the  air,  and  moving  as  currents  of  electricity, 
than  to  their  original  formation.  Electric  potential  gradients 
are  due  to  a  separation  of  the  positive  and  the  negative 
charges,  and  ultimately  the  source  of  this  energy  will  go  back 
to  some  transformation  of  gravitational  force.  At  present,  the 
inquiry  culminates  in  the  necessity  of  accounting  for  the 
negative  charge  of  the  earth,  which  is  doubtless  a  very  difficult 
problem.  I  shall  make  the  following  suggestions  regarding  it. 

THE  NEGATIVE  CHARGE  OF  THE  EARTH. 

Elster  and  G-eitel's  theory  of  the  atmospheric  electric 
potential  assumes  that  the  negative  ions  when  produced  in  the 
atmosphere  move  to  the  earth,  which  is  a  conducting  body, 
more  rapidly  than  the  positive  ions,  and  that  their  accumula- 
tion upon  it  produces  the  observed  charge.  This  surface 
charge,  it  is  inferred  from  Linss's  experiments,  now  verified, 
dissipates  at  the  rate  of  discharging  itself,  on  the  average,  in 
100  minutes.  But  the  researches  of  Simpson  (Phil.  Mag.  6, 
689,  1903)  Ebert  and  Ewers  (Phys.  Zeits.  5,  No.  5,  p.  135-140) 
throw  doubt  upon  this  view,  because  they  have  not  been  able 
to  show  that  a  conductor  in  ionized  air  receives  any  charge 
by  the  absorption  of  either  kind  of  the  ions  surrounding  it. 
Ebert,  on  the  other  hand,  seeks  to  supply  the  surface  charge 
of  the  earth  by  referring  the  source  to  radio-active  con- 
stituents within  the  earth,  which,  discharging  through  the 
porous  ground  by  the  capillary  action  of  the  narrow- channels, 
deposits  the  negative  charges  on  the  sides,  while  the  positive 
charges  are  ejected.  It  is  not  clear  that  this  process  is 
applicable  to  the  great  oceanic  areas  of  the  earth,  though  these 
show  about  the  same  electrical  gradients  as  the  land  areas, 
nor  would  this  process  appear  to  allow  the  negative  ion 
contents  to  accumulate  sufficiently  in  the  strata  of  the  air  at 
some  distance  above  the  ground,  to  produce  the  high  tension 
observed  in  lightning  discharges  and  in  nondisruptive 
strains. 

There  ai-e,  however,  several  other  processes  which  probably 
contribute  to  the  separation  of  the  positive  and  negative  ions, 


22 


by  which  the  former  tend  to  accumulate  in  the  atmosphere 
and  the  latter  at  the  surface  of  the  earth. 

(1)  The  different  masses  of  the  +  ions  and  the  —  ions,  the 
-f  ions  being  much  larger  than  the  —  ions,  may  have  a  differ- 
ential I'elation  to  the  mechanical  light  pressure  due  to  electro- 
magnetic radiation,  and  it  is  possible  that  the  negative  charges 
are  driven  before  it,  within  the  earth's  atmosphere  itself,  more 
abundantly  than  the  positive  charges.     If  the  incoming  solar 
radiation  produces  +  ions  and  —  ions  excessively  upon  im- 
pact with  the  top  of  the  aqueous  vapor  arch,  which  is  near  the 
surface  of  the  earth  in  the  polar  zones  and  high  above  the 
ground  in  the  Tropics,  then  the  —  ions  may  be  driven  to  the 
•earth  by  the  mechanical  pressure  of  the  light,  while  the  -f  ions 
tend  to  remain  in  the  higher  strata.     Although  this  is  not  quite 
parallel  to  the  case  of  the  formation  of  cathode  streams  in 
rarefied  gases  or  the  comet  tails  in  free  space,  there  may  be 
some  differential  action  of  this  kind  that  tends  to  separate 
these  two  kinds  of  ions,  carrying   the  negative  ions  to  the 
earth. 

(2)  Since  fresh  ions  are  produced  in  some  way  by  the  radia- 
tion in  the  existing  electrostatic  field,  V,  surrounding  the  earth, 
therefore  the  velocity  of  the  motion  of  the  nucleus  carrying  the 
charge,  e,  where  the  radius  of  the  nucleus  is  R  and  the  viscosity 
of  the  air  is  /*,  is  determined  by  C.  Barus  from  the  formula, 

Ve 
u—        '    .    (Science,  January  2, 1903.) 

4-/.4/1 

For  R  =  10-",  //.  =  0.0002,  e  =  200  x  7  X  10~10  E.  S.  V.,  v  =  37 
cm/sec  =  0.8  mile  per  hour,  for  the  unit  electrostatic  field 
=  0.003  mile  per  hour  for  a  field  of  1  volt/cm.  Hence,  by 
changing  the  sign  of  e,  the  ion  charge  in  the  formula,  those 
of  one  sign  would  be  driven  in  one  direction  and  those  of  the 
other  sign  in  the  opposite  direction.  This  is  evidently  one 
true  cause  of  the  observed  separation. 

(3)  Similarly,  the  -f-  ions  and  the  —  ions,  being  generated  in 
the  free  air  by  radiation  in  the  midst  of  the  magnetic  field 
surrounding  the  earth,  should  be  driven  in  opposite  directions 
along  the  lines  of  force  to  the  polar  regions.     As  the  electro- 
static field  tends  to  separate  a  swarm  of  +  ions  and  —  ions  in 
radial  directions,  the  +  ions  to  higher  strata  and  the  —  ions 
to  earth,  so  the  magnetic  field  tends  to  send  +  ions  to  one 
polar  region  and  the  —  ions  to  the  opposite  polar  region.     In 
fact,  these  electric  and  magnetic  lines  of  force  are  the  natural 
highways  of  travel  for  the  ion  content  of  the  air,  and,  in  a 
word,  it  is  my  opinion  that  the  ions  are  generally  moving 
about  from  one  place  to  another  while  they  are  free  from  the 
bonds  of  atomic  and  molecular  combination.     Of  course  the 
temperature,   vapor  content,   and  pressure  may  accelerate  or 
impede  these  movements,  as  has  already  been  pointed  out  by 
Elster  and  Geitel,  Ebert,  Gockel,  and  others,  and  so  introduce 
the  meteorological  conditions  which  have  been  observed.     The 
ions  in  this  way  become  sensitive  registers  of  the  physical  vari- 
ation in  the  atmosphere,  and  have  much  interest  to  the  meteor- 
ologist. 

(4)  There  is  yet  one  more  cause  for  the  earth's  electric  sur- 
face charge  which  may  be  the  most  important  of  all,  and  that 
exists  inside    the  earth   in   the  atomic  circulation  within    its 
mass.     W.  Sutherland6  has  indicated  that  the  static  electric 
charge  of  the  earth,  and  its  magnetic  field  may  be  due  to  a 
slight  displacement  of    the  positive  and    the    negative    body 
charges,  through  a  distance  comparable  to  the  diameter  of  a 
molecule,  lO^cm.,  whereby  the  negative  charge  of  the   earth, 
as  a  whole,  is  that  distance  farther  from  the  center  than  the 
positive  charge.     There  seems  to  be  much  difficulty  in  under- 
standing how  this  takes  place  physically  in  the  earth,  which 
should  apparently  be  electrically  conducting  under  high  tem- 
perature and  pressure,  but  it  may  be  possible  to  escape  from 

•A  possible  cause  of  the  earth's  magnetism,  Terr.  Mag.  June,  1900. 
June,  1903.    December,  1904.     W.  Sutherland. 


this  criticism  by  resorting  to  the  following  modified  conception 
of  a  dynamic  rather  than  a  static  character. 

It  seems  to  be  probable  that  atoms  of  matter  are  constituted 
of  negative  ions  circulating  rapidly,  in  connection  with  a 
larger,  more  inert  positive  charge,  either  inside  or  outside  of  it. 
The  velocity  of  rotation  of  the  —  ions  is  greater  than  the  +  ions 
and  this  would  imply  that  there  is  a  tendency  for  some  of  the 
negative  ions  to  pursue  paths  of  larger  radii  than  the  positive 
ions,  and  also  at  greater  angular  velocity.  Thus,  they  ought, 
in  one  way  or  another,  to  recede  farther  from  the  center 
of  the  earth  than  the  positive  ions,  but  in  so  far  as  their 
natural  orbital  motions  are  impeded  they  will  tend  to  accumu- 
late and  become  static  charges  nearer  the  surface  of  the  earth. 
If  these  circulating  ions,  the  negative  ions  moving  more  vigor- 
ously, have  a  tendency  to  become  polarized  as  to  their  orbit, 
that  is  to  circulate  in  planes  perpendicular  to  the  axis  of  the 
rotation  of  the  earth,  through  the  effect  of  the  earth's  deflect- 
ing force  due  to  its  own  angular  velocity,  then,  there  should 
be  integrated  a  resultant  true  magnetic  field  directed  from 
north  to  south  through  the  interior  of  the  earth.  It  is  quite 
likely  that  Southerland's  view  can  be  modified  from  the  electro- 
static basis  proposed  by  him  to  this  electrodynamic  basis,  with 
resulting  static  negative  residual  charge  at  the  earth's  surface, 
and  magnetic  field  within  the  earth,  sustaining  that  observed 
outside  of  its  surface.  Should  this  be  the  case,  it  must  be  in- 
ferred that  similar  processes  go  on  in  the  sun  and  the  stars,  and 
that  all  large  rotating  celestial  bodies  are  polarized  magnetic 
spheres,  with  electrostatic  charged  surfaces.  The  variation 
of  the  distribution  of  these  charges  from  time  to  time,  and 
from  region  to  region,  constitute  the  source  of  the  periodic 
and  aperiodic  disturbances  with  which  we  are  becoming 
familiar  in  several  different  classes  of  observations.  To  what- 
ever extent  these  processes  are  in  operation  within  the  earth 
and  in  its  atmosphere,  as  here  outlined,  and  thus  cause  the  ob- 
served general  distribution  of  the  positive  electric  charge  in 
the  higher  strata,  with  the  negative  charge  at  the  surface  of  the 
earth,  we  may  properly  consider  the  variation  of  the  electric 
gradients  in  the  atmosphere  as  a  phenomenon  resulting  there- 
from, in  consequence  of  changes  in  the  temperature  conditions 
in  the  earth  and  in  the  atmosphere. 

THE     PERIODIC     VARIATIONS  OP     THE    ELECTRIC    POTENTIAL  GRADIENT 
IN  THE  EARTH'S  ATMOSPHERE. 

I  have  called  attention  to  the  fact  that  the  electric  poten- 
tial gradient  varies  from  year  to  year  inversely  to  the  solar 
prominence  numbers,  and,  in  consequence,  inversely  to  the 
strength  of  the  solar  radiation,  insolation,  and  terrestrial 
temperatures.  An  increase  of  the  temperature  of  the  lower 
atmosphere  decreases  the  potential  tension  between  the  masses 
of  the  positive  and  of  the  negative  ions.  Similarly  the  poten- 
tial gradient  is  greater  in  the  polar  regions  of  the  earth  where 
the  air  is  cold,  than  at  the  equator  where  it  is  warm.  At  any 
given  station  the  gradient  is  greater  in  winter  than  in  summer. 
Generally,  cooling  the  air  is  favorable  to  producing  an  increase 
of  the  electrical  gradient.  Likewise,  it  will  be  seen  by  referring 
to  figs.  26-37,  50,  52,  53,  54  that  the  diurnal  maxima  of  the  elec- 
tric potential  occur  at  the  times  of  the  true  minima  of  the  tem- 
perature waves,  8  a.  m.,  8.  p.  ni.,  or  as  modified  by  the  cor- 
relative pressure  maximum  waves  occurring  two  hours  later, 
10  a.  m.,  10  p.  m.  We  may,  therefore,  conclude  that  one  uni- 
form physical  process  is  concerned  throughout  this  series  of 
electrical  gradient  transformations,  namely,  the  air  in  cooled  in 
some  ivay  whenever  there  is  an  increase  of  the  electrical  gradient. 

(5)  It  seems  to  me  but  a  step  to  arrive  at  an  equally  general 
and  valid  theory  of  the  variation  of  the  electric  potential.  We 
need  only  admit  that  the  positive  ions  have  a  stronger  affinity 
for  a  gas  at  low  temperature  than  for  the  same  gas  at  a  higher 
temperature.  If  the  +  ions  seek  regions  of  low  temperature 
and  the  —  ions  move  to  the  regions  of  high  temperature,  we 
have  yet  another  cause,  in  addition  to  the  four  already  men- 


23 


tioned  for  the  separation  of  the  positive  and  the  negative  ions 
into  two  masses.  Hence,  in  the  diurnal  waves  of  temperature 
the  positive  ions  flow  downward  from  their  normal  level  to  a 
lower  level  as  the  minimum  of  the  temperature  wave  in  the 
lower  strata  passes  over  the  place.  This  implies  that  at  the  8 
a.  m.  and  8  p.  m.,  local  hours,  a  stream  of  +  ions  is  directed 
downward,  so  that  the  positive  ions  as  a  mass  approach  more 
nearly  the  surface  of  the  earth  where  the  negative  ions  are 
already  accumulated.  Hence,  the  potential  gradient  of  elec- 
tricity will  be  increased  in  proportion  to  this  approach.  It 
seeins  that  the  negative  stratum  may  be  considered  as  quite 
steady  in  elevation,  while  the  positive  stratum  rises  and  falls  in 
a  wave,  synchronously  with  the  passage  of  the  temperature 
•wave.  Referring  to  Section  III,  fig.  54,  the  temperature  curve 
of  Section  I  has  been  plotted  once  more  in  the  reverse  position, 
to  show  the  approach  of  this  cold  stratum  to  the  earth.  From 
this  exposition  of  the  facts,  I  assume  that  a  current  of  +  ions 
descends  at  8  a.  m.  and  8  p.  m.  with  the  temperature  wave, 
and  that  the  same  ions  ascend  at  3  a.  m.  and  3  p.  m.,  while  the 
—  ions  remain  all  the  while  at  about  the  same  level.  This, 
evidently,  causes  the  observed  increase  and  decrease  of  the 
electric  potential  as  observed  at  the  surface  during  the  24 
hours  of  the  day.  I  see  in  the  movement  of  the  +  ions  from 
one  elevation  to  another,  while  the  —  ions  remain  on  or  near 
the  charged  surface  of  the  earth,  the  true  cause  of  the  diurnal 
variations  of  the  atmospheric  electric  potential  gradient. 
TABLE  3. — Diurnal  variation  of  the  vapor  tension  at  Pure  St.  Maur,  Paris. 


TABLE  5.— Diurnal  variation  of  the  vapor  tension  at  Blue,  Hill,  400-meter  level. 


Hours.           a     1    4          =' 

"   |  £      a 

°C           !>> 

1 
'=          i 

3              3 
•-a           *-a 

1 

/ill 

12  a. 

-  .13  -  .OsU  . 
+  .14       .00-. 
-  .13-  .06-  . 
+•  .09—  .10-  . 
-  .01  -  .14-  . 
-  .12-  .17-  . 
—  .  19  -  .  19  -  . 
-  .22-  .20—  . 
.22          v> 

01  —  .09;+  .10 

0>—  .15  -  .13 
03  21  17 

-.46-  .11 
-  .51—  .48 
—  .59—  .74 
—  .64—1.01 
—  .73—1.11 
—  .73-1.11 
—  .  73  —1.  08 
-  .64-1.01 
—  .  46  -  .  74 
—  .  28  —  .  52 
—  .05—  .30 
+  .29—  .05 
-  .  59  -  .27 
+  .95+  .48 
+  1.11+  .74 
+1.44+.89 
-1.49  -1.  00 
-1.16  -1.07 
-  .64  +1.00 

-  .  oa  -  .94 

-  .  19  -  .  74 
—  .  37  +  .  50 
—  .41+  .22 
1—  .54—  .03 
—  .46—  .11 
7.43   10  10 

-.19 

—  .30 
—  .53 
-  .70 
-  .82 
—  .93 
—  .82 
—  .70 
—  .53 
-  .36 
-  .01 
r  .26 
+  .48 
+1.01 
+1.29 
+1.47 
+1.24 
+  .80 
-  .42 
-  .11 
—  .19 
—  .30 
—  .30 
-.30 
—  .19 

9.57 

-  .20T  .22+  .12-  .13 
-r  .  31  +  .  29  +  .  18  +  .  16 
-  .31+  .31  +  .  23+  .17 
-  .26  -  .31+  .25-  .17 
+  .09  +  .34  -  .25+  .16 
—  .  07  +  .  09  —  .  13  -  .  07 
—  .23—  .06—  .12—  .01 
—  .45—  .18—  .19—  .10 

1 

•>. 

3 

06  25  1'i 

4 

08  31  10 

5  

11  -  .31  -  .12 

15-  .31  —  .32 
19—  .29]-  .55 

21  —  .221—  .64 
17—  .15  —  .65 
10—  .03—  .48 
02  -  .  10  —  .  15 
11  -  .27  -  .10 
Ai  -  .47  .:.« 
24  -  56+  .51 
25  -  .  63  -  .  58 
27+53  51 

6  

8. 

9 

.20         ""O 

—  .49—  .29—  .21—  .16 
-  .28—  .24—  .12—  .16 
—  .01  —  .09—  .07—  .16 
-  .434-  .03—  .02—  .15 
•j-  .48+  .12—  .02-  .15 
+  .54.+  .12—  .04—  .14 
+  .  54  +  .  09  —  .  08  —  .  12 
+  .41+  .03-  .12-  .10 
+  .22—  .09,—  .12'-  .07 
—  .12—  .18—  .12,-  .02 
33'        29         10   '      0"' 

10. 

—  .15—  .15-  . 
—  .06—  .03—  . 
06          11 

11 

12  p. 

1* 

-  .13-  .17  -  . 
-  .15  -  .21  -   . 
-  .09-  .21  -  . 
-  .  13  ,-  .  22    -  . 
+  .08+  .20  +  . 
+  .03+  .14-  . 
-  -  02  +  .  08  +  . 
05         05 

2 

3 

4.   . 

5  

24  34  35 

6  

17  -  .2.5  -  .17 
09  05  03 

7  ... 

8 

01  —  .11  —  .12 
04  -  .  15  —  .  12 
OSi—  .15—  .12 
04—  .13—  .12 
Oil—  .09  -  .10 

74  a  02  5.  40 

9 

05         01 

10  

-  .  03  -  .  02  —  . 
-  .  04  -    03  —  . 
+  .13+  .06  +    . 

1.59     1.57     1. 

—  .49—  .09+  .13-  .11 
—  .17  +  .12  +  .12-  .14 
+  .20-  .22+  -12  -  .13 

8.321     4.45      3.14      1.90 
1             1             1             1 

11 

12  

Means... 

TABLE  6. — Diurnal  variation  of  the  vapor  tension  at  Slue  Hill, 
luoo-meter  level. 


Hours. 

c 

s 

!•! 

:TJ 

u 

7. 

- 
~ 

>. 

g 

3 
it 

£ 

3 
-: 

+  .14 

+  .08 

It 
p 

i 

,;             V 
Q                 O 
f                X 

-.191-  .17 

-  .  18  -  .  16 

^           12  a      

a         i 

~            2  

12  a 

—  .ia 

-  .08 

0.0 

+  .08 

+  .oT 

+  .23+.  17 
-  .16-r  .03 

+  .18 
—  .01 

+  .16 

i  .16 

—  .02 
—  .09 

3  
102         4  

1 

07        5  

2 

6    

j 



1  

7.. 

-  .14 
—  .18 
-  .17 
-  .21 
-  .17 
—  .12 
—  .01 
-  .05 
-   .10 
-  .13 
-  .13 
+  .18 
+  .19 
+  .« 
+  .18 

12 
-  .07 
+  .OS 
—  .05 

-       - 

i:S 

-  .21 
—  .  17 
—  .07 
+  .01 
-  .06 
-  .06 
-  .06 
-  .06 
-  .05 
+  .08 
+  .12 
+  .09 
+  .13 
+  .10 
-  .10 
+  -04 
+  .01 

-  .08 
-.15 
-  .18 
-.11 
-  .01 
+  .09 
-  .  T2 
-  .09 
-  .03 
—  .04 
-  .11 
—  .13 
—  .14 
—  .10 
4-  .01 
+  .09 
+  .13 
.12 
-  .09 
+  .08 

-  .  03  —  .  16 
—  .02—  .19 
—  .07       .00 
U  +  .22 
+  .  30  .  -  .25 
-  .  24  +  .  18 
+  .09+  .04 
-  .12—  .10 
-  .  20  -  .15 
—  .  26  —  .  30 

So           9ti 

—  .23 
—  .26 
-  .07 
+  .12 
+  .26 
M 
+  .10 
-  .10 
-  .30 
—    29 
-  .XI 

=  :S 

-  .08 
—  .10 
+  .24 
+  .39 
+  .39 
+  -32 
+  .24 

-  .18 
-  .23 
-  .01 
+  .21 
+  .34 
+  .38 
+  .32 
+  .09 
-  .18 
-.28 

-'•"« 

-  !26 
+  .09 
+  .31 
-  .25 
+  .21 
4-  .17 

-  .08. 
—  .15 
.00 
+  .27 
+  .43 
-    .44 

ll 

ll 
-  .64 

—  !l4 

- 
•    .24 
-.27 
-  .24 
4-  .22 

—  .45 
—  .55 
—  .56 
—  .25 
+  .14 
+  .38 
-  .42 
+  .19 
-  .04 
-  .14 

z;;t; 

-  '.K 
+  .38 
+  .33 
-  .27 
+  .18 
+  .11 

-.42 

—  .  56 
—  .53 
—  .24 

-   .12 
+  .28 
33 

—  .18 
—  .34 
-  .37 
—  .37 

—  !io 

07 

18        8    



_  .22        9  
20       10          .... 

-  .21       11  
22       12  p  

9 

13         1  

10 

01         2 

11 

+  .22 
-  .24 
+  .28 
+  .24 

t:i47 

—     2S 
-  'l~7 
-  .10 
+  -07 
-  .02 
—  .05 
—  .07 

4.    08        3  

,2,, 

-  .22 
-  .25 
+  .24 

+  .25 

-  .27 

-  !40 
+  .29 
+  .19 

-  .11 
-  .01 

- 

+  .09        4  
+    09        5... 

•> 

-L    15        6  

3  

4 

—  '.41 
—  .40 
-  .22 
-  .01 

-  '.*-< 
+  .21 

-  .36 
!39 

+  .20         7  ... 
+    *2         8 

5  
6 

—  .33 

-  .22 

t:S 

-  .  29 
-  .47 

-     . 

+  .15        9  
I  .  14       10  

7 

+     13       11 

g 

+    08       12 

9 

+  .06 
.00             Means... 

-  .02 

10 

11  .. 

Hours.           o         * 

-?         .1 

u 

« 
< 

K 

1 

| 

*^ 

•^ 

3 
n 

M 

3 
•< 

1 
I 

8 

> 

o 

fc 

0 

1 

+  .211 

+  .17  + 

-r.osU 

-  .03  - 

—  .09  — 

-  .11- 

—  .17  — 

—  .22  — 

-  .  2U  - 

—  .16  — 

15  — 

15  — 

16  — 
14  — 
14  — 
11  — 
09  — 
011- 

—  .09  — 

-  .19  + 
+  .23  + 

-  .24  - 
+  .23- 
+  .24  + 

-  .  21  - 


1.37 


12+  .1 


.07  - 
.01  — 
.04  — 
.07- 
.09  — 
.07  — 
.05  — 
.07- 
.07  — 
.08  — 
.09  — 
.09  — 
.07  — 
.04  — 
.01  + 
.02- 
.01  - 
.01  - 
.05- 
.06  + 
.11-r 
.14  - 
.12  - 


.08  — 
.00  — 
.08j— 

09  — 
,09  — 
,03  — 

02- 
.05  — 

09  — 
,10  — 

;-•    - 

16  - 
10- 
05- 

,01  - 
03  + 

,02  + 
03- 
01  + 

06  4- 
13  - 

17  - 

18  + 
16  + 


.06  + 
.05- 

.15- 
.22  — 
.26  — 
.24  - 
.20  — 
.14  — 
.09  — 
.10  — 
.06  — 
.02- 
.07  + 
.07  + 
.06  + 
.07  + 
.13  + 
.17'  + 
.14,+ 
.12'  + 
.14  - 
.10  + 
.13- 
.13  + 
.06  + 


16- 

42- 
53-1 
67-1 
80j— 1 
74-1 
72  — 


31,—  .15'+  . 
68  —  .  49  —  . 
96—  .Ct—  . 
S»— 1. 
.64—1. 
ZOO— 1. 


1.73     2. 


43- 
09  + 

041  + 

38  + 
52^1 
51+1 
61-1 

n  : 
51K1 
43  + 
37- 
37  - 
37  - 
23- 
09  — 


211+.26+.34       .( 

24  -  .17+  .27—  .( 
S4  —  .  03  +  .  10  —  .  1 


84  -\. 
55—1. 


.19  - 
96  — 
62  — 

27  -  .  95J-  . 
04  —  .  37!  -  . 
44  -  .06!+  . 
61  -  .  V.<  -J-  . 
94+  .741+1. 
21  -1.26 
28+1.51 
37  -1.64  .. 
24+1.' 
05+1.70 
71  +1.64  -  . 
43+1.29+  . 
08+  .91  +  . 
04+  .53  -  . 
27+  .09+  . 
31—  .15+  . 

8.73     8. 


00  +  .22 
03+  .20 

..  16 +.07 

28  —  .31  —  .  09  —  . :«  —  .06 
56—  .62—  .27i—  .33!—  .11 
>'—  .87—  .42—  .44—  .17 


49  —  .  94  —  .  37  —  .  44 
27-  .88  -  .36—  .44 


—  .21 

-  .29 


90—  .78—  .3K-.29—  .26 
53  —  .  481—  .  27  —  .  13  -  .  20 
10—  .18  -  .21+  .04-  .14 
28+  .14—  .08+  .10—  .09 
63+  .46+  .06+  .19—  .05 
04-  .55-  .  ?2+  .34  —  .05 
22  +  .95+  .22+  .32—  .03 
34+  .95-  .1*+  .32+  .01 
21  -1.05  -  .12+  .28  +  .02 
09+  .654-  .03+  .20+  .05 
85+  .56+  .03!+  -15+  .06 
55  -  .43  .00+  .10  -  .11 
38+  .20—  .03+  .10+  .17 
21  +  .10+  .06+  .08+  .19 
02  +  .24-j-  .19+  .08-1-  .21 
09  +  .23+  .35+  .05+  .22 
21  +  .26+  .34  .00+  .22 


12. 


.!—  .10       .OOJ+  .08  + 


.17  -  .18  + 


Means...'    5.33     5.21     5.15 


i—  .02—  .19—  .17;—  .02 


6.07     7.5<J    10.10    11.44    11.20     9.99     7.99     6.29     5.43 


6.42     4.37     2.91      1. 


TABLE  4. — Diurnal  variation  of  the  vapor  tension  at  Blue  Hill,  195-meter  level. 


TABLE  7. — Diurnal  variation  of  the  atmospheric  electric  potential,  Greenwich 
observations,  on  an  arbitrary  scale.     Clear  days. 


Hours. 

d 

n 
~i 

"— 

^ 

B 

— 

- 

i           .• 
=          — 

•z           = 

-5        |       -> 

?         ? 

>          -t                Hours. 

7-.           - 

1 

1 

3 

- 
— 

it 

f 
a 

3 

a 

= 

3.        -         i          ^ 

7      *      ; 

X             —             ^            — 

12  a 

-  .85 

-    -72 

~  '.33 
+  .14 
+  .04 
-  .08 
—  .25 
—  .31 
—  .43 
-  .46 
—  .52 
—  .51 
-  .50 
—  .49 
—  .49 
-  .47 
-  .38 
-  .23 
—  .12 
-  .04 
-    34 
-  .54 

+  .85 
2.06 

-  .71 
—     6' 
-  '.52 
+  .36 
1 

—  !io 

—  .21 
—  .35 
—  .47 
—  .51 
—  .49 
—  .54 
—  .48 
—  .43 

27 

—  !l9 
06 

-  .75+1.14 
+    -67  -   .  91 
+  .47 
-  .33  -  .47 
-  .21   4-  .21 
+  .03  -r  .15 
—  .10—  .06 
—  .30-  .11 
—  .37  -  .29 
—  .  56  —  .  23 
—  .  57  —  .  32 
—  .  59  —  .  29 
—  .56—  .38 

+  -92 

+  .87 

7- 

+  .65 

-  .08 
—  .33 
—  .57 
46 

-1.12  -  .75 
+  .80+  .56 

t  .m+  .  55 

—  .  04          24 
-  .11        .1" 
16          01 

+  .95'+  .40 
-  .40  -  .39  -   .39 
—  .10  -  .11  -  .22 
—  .30—  .17  -  .05 
-  .43-  .44\—  .08 
-  .  4'.'  —  .  71  —  .24 
-   .  74  -  .  94  —  .  43 
46  -  1  07          60 

-r    50         45       12  a      ... 

i  i  i7T77i  i  i  ++++++++++++++  i 

—  4 

—12 
—14 
—14 

—13 
-12 
—  6 

—  4 
—  1 
+  8 

' 

=i 

+  2 

4-  6 
-  8 
-10 
^12 
-10 
--    7 
' 
-  3 
—  3 

84 

+  4 

—  7 
—  9 
—  9 
—  7 
—  4 
0 
+  2 
-   2 
-r  6 
4-  4 
—  2 
—  5 
—  7 
—  8 
—10 
—  3 
-  2 
+  8 
-11 
-10 
-10 
-  5 
—  2 

73 

+  6 

+  * 
—  1 
—  4 
—  5 
-  2 
+  2 
-  9 
+11 
+  6 
-   1 
—  3 
—  9 
—11 
—10 
—10 
—  9 
-  6 
—  3 
0 
+  5 
+  7 
+  9 
-  5 
-  1 

66 

+  4 
0 
—  3 

-  6 
—  8 
—  7 
—  2 

-  7 
-10 
4-  3 
+10 

+  4 
6 

-  6 

- 
0 
—  2 
—  2 
0 
+  « 
+  1 

+  3 
—  2 

—  9 
9 

—  6 

-  4 
—  3 

^_    J 

+  6 
+  11 
-t-10 

+  6 

1  1  1  1  M  1  M 

+  « 

+  3 
+  1 

—  4 
—  4 

:i 

+  3 

Ei 

—  8 
—  8 
—  7 
—  2 

+  4 
+  8 
-10 

h 

45 

0 
—  5 
—10 
—11 

-11 
-14 

—13 
—10 

-  7 
—  2 
- 

-  4 
-  1 
—  1 
—  1 
-   1 
- 
-11 
-13 
12 
-  9 
+  6 
-  3 

49 

—  1 

—  4 
7 

—  9 
—10 

—12 

—12 
-13 

-  7 
-  1 
+  5 
0 
+  2 
4-  2 
-  4 
-  9 
-14 
-14 

+  7 
+  8 

+  4 
-   1 

56 

—  2 

—  7 
—  6 
—  8 
—  8 
—  8 

—  3 
—  1 

0 
+  9 

-  5 
+  8 

-  2 

-  3 

+  4 
-  6 
+  6 
-    4 
-r  3 
+  4 
-   5 
+  2 

49 

- 
—  2 

-14 
-14 

—12 

—  9 
—  7 
—  3 

+ 

4- 
- 
+  5 
+  6 
-   7 
+  5 
+  4 

+  9 

+  6 

- 

71 

1 

_j_     4g  -j-     45         1               .   

2 

42          43         2 

3 

SI          34         3              ... 

4  
5 

-   .11  -  .27         4  
03         12        5 

5 

47          21 

16         00        6 

7 

—  .50—  .41 

24         57 

36         10        7 

g 

56          **3          59 

45         19        8 

9  
10 

—  !37 
—  .39 
-  .33 
—  .37 
-  .43 
-  .35 
—  .37 
—  .33 
—  .42 
—  .37 
—  .05 
—  .02 
-  .41 
-  .79 
-  .92 

6.39 

—  .31   -  .69 
-  .05—  .34 

—  .14—  .11 
+  .  22  -   .41 

—  .  41  —  .  49i—  .  52 
-  .02  -    .(13,-  .40 
+  .2SJ-1-  .26—  .  lit 
.-   .46—  .10 
-  .  53  -  .  5.-- 
-  .  68  —  .  55  -  .113 
22          3: 

-  .42—  .23        9  
27         28       10         

11 

!•>         22       11        

'4         28       12  p 

—  8 
—  9 
—  9 
—  5 

:i 

i 

+  10 

-r   6 

+  2 
60 

•> 

46 

—  .65 
—  .67 
—  .60 
—  .58 
66 

—  .01 
-   .  0*  —  .11 
—  .  25  —  .  20 
—  .  46  -  .4.5 
—  .24—  .66 
41         63 

i<'7          30         2              .    ... 

3 

4] 

17         30        3 

4 

-  .20 
—  .14 
—  .09 
—  .01 
-  .09 
+  .32 
+  .60 
-  .65 
+  .75 

2.63 

+  .19|+  .11—  .01 
—  .16  +  .OS-  .02 
—  .  17    -  .17-  .1-4 
—  .481-  .11  —  .06 
-  .  26,—  .  08  —  .  03 
10          17  —     10 

34         29        4             

5  
6 

—  .  24  —  .  25         5  
•'«         20         6 

7 

48 

28         17        7 

g 

—  .03 

-   .22 
-  .47 
-' 
+  .71 

2.13 

—  .39 
06 

-  .  45  -  .  55 
—  .  10  -  .0.5 
+  .33  -  .12 
-  .  52  4-  .  79 
+  1.  12  -  .  75 

9.49    12.37 

21         12        8 

9 

10  '      OS        9 

10     . 

-  .46 
-' 
+  1.14 

3.78 

.26  -  .34 

11.  76     8.  CU     4.  If 

—     (4  -     18       10    

11  
12  

-  .16  -  .87      11  
51  1         45       12       

Means... 

3.29     2.16             M.-ans... 

24 


TABLE  8. — Diurnal  variation  of  the  atmospheric  electric  potential;  Green- 
wich observations;  rainy  and  clear  days. 


TABLE  9. — Annual  variation  of  Hut  almoxpheric  ekctric  potential;  Greenwich 
observations;  on  an  arbitrary  scale. 


Hours. 

d 

a 

£ 

k 

1 

*C 

a 

tft 

w 

a 

a 

a 
>-> 

>, 

3 

t<i 
1 

I 

I 

> 

o 

'K 

| 

12  a 

0 

ft 

-)-    1 

+  4 

+  5 

+  7 

+  6 

+  6 

4 

1 

o 

+  3 

1  

-  7 

—  3 

—  2 

+  3 

+  2 

+  5 

+  3 

+  3 

—  3 

—  5 

—  8 

3 

2  

-  9 

__     Q 

—  5 

—  3 

—  3 

0 

+  s 

—  6 

—  6 

—  4 

—10 

4  
5    

—14 
—13 

—12 
—12 

g 
—  6 

—  6 

—  7 

-  9 

g 

- 

—  5 
—  2 

-  3 
—  3 

—10 

—12 

—10 
11 

-  7 
—  7 

—14 
14 

6  

—14 

—10 

—  3 

—  5 

—  5 

_  1 

_  2 

—  12 

—  12 

7 

—  12 

7  

—10 

—  6 

+  2 

+  2 

+  4 

-f 

+  2 

0 

9 

8 

5 

6 

8    

—  8 

—  4 

+  6 

+  6 

+  6 

+  2 

0 

—  6 

7 

—  4 

—  2 

5 

0 

+  2 

+  1 

+  4 

3 

_j_  i 

I 

1 

2 

3 

4.  i 

10... 
11  
12p     . 

+  5 
+  8 
+  4 

+  6 
+  9 
+  1 

+  6 
+  2 
0 

o 
2 
—  G 

+  4 
+  2 
—  6 

+  4 
-  2 
_  2 

+  9 

+  5 
0 

+  6 
+  3 

4-  i 

+  6 
+  7 
-t-  2 

+  4 
+  3 

+  2 
+  3 

+  2 

+  6 

+  6 
+  4 

1. 

+  6 

0 

0 

—  5 

—  8 

—  6 

—  6 

7 

-(.  1 

0 

-|-  1 

-|-  i 

2 

+  5 

1 

3 

2 

10 

8 

9 

5 

1 

0 

_j_  j 

4-  2 

3  

+  6 

+  2 

_  2 

_  4 

6 

—  3 

g 

—12 

1 

+  2 

+  3 

+  2 

4      

+  8 

+  8 

—  4 

—  4 

2 

4 

—  6 

—  6 

-|-  1 

+  9 

+  3 

+  4 

5      

+  6 

+  7 

+  2 

—  3 

-)-  1 

—  4 

—  7 

—  5 

+  6 

+10 

+  3 

+  7 

6 

+  8 

+  9 

+  7 

-j.  i 

_j_  i 

2 

1 

+  2 

+  9 

+  12 

_L  4 

-t-  8 

7  

+  18 

+  9 

+  8 

+  7 

+  6 

-)-  1 

2 

+  3 

+  10 

+  9 

+  5 

+  7 

8        

+  6 

+  7 

+  5 

+  9 

+  8 

+  3 

2 

+  4 

+  8 

+  5 

+  4 

+  2 

9  :. 

+  4 

+  6 

+  6 

+  6 

+  9 

+  6 

+  6 

+  7 

+  6 

+  5 

+  3 

+  9 

10  

+  5 

+  6 

+  6 

+  11 

+  12 

+10 

+10 

+13 

+  6 

+  7 

+  4 

+  8 

11     .... 

-f-  4 

+  3 

+  2 

+  10 

+  11 

+  9 

+  9 

+  9 

+  3 

+  s 

+  2 

+  3 

12  . 

+  1 

—  8 

—  1 

1-  4 

+  s 

+  $ 

+  6 

+  5 

0 

2 

2 

+  2 

Means... 

62 

68 

62 

56 

52 

87 

42 

39 

44 

47 

43 

53 

Years. 

All  days. 

Rainy 
days. 

Clear 
days. 

Factor. 

All  days. 

Rainy 
days. 

Clear 
days. 

1881  

262 

524 

1882 

210 

121 

287 

420 

242 

1883 

264 

152 

340 

528 

304 

1884 

236 

117 

299 

472 

234 

1885 

234 

85 

3^8 

fX  2  = 

170 

1886 

224 

127 

301 

448 

254 

1887 

305 

176 

388 

610 

770 

1888  

285 

169 

370 

570 

338 

740 

1889  

1890  

629 

433 

795 

1891  

542 

376 

670 

1892  

465 

332 

557 

1893  

553 

421 

663 

1894  

514 

358 

661 

1895  

761 

623 

880 

18%  

661 

516 

768 

1897  

586 

459 

679 

1898  

483 

342 

553 

1899  

343 

184 

432 

1900  

450 

338 

539 

1901  

593 

417 

680 

In  my  next  paper  I  will  show  that  this  action,  at  the  same 
time,  produces  the  diurnal  variation  of  the  magnetic  field  as 
observed  at  the  surface  of  the  earth. 


K 

w 
K 

4 

1 

I 

* 

•N? 

5 

Xi 

1 

5S 

1 
^ 

c 

5 

6 

N» 

§ 

^ 

'2*A.    %         4          ff         S         70      7SF    S         4          6         a        70        7% 

Fig.  5J. 
January 

February 
JvfarcA 
April 
Afay 
t/itrtf 
July 
August 
iSeptem&e. 
October- 
ffcv&miier 
December 

f-ro 
•f-f 
o 
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Clear-  c£<xy&. 
dear-  T*-il!?t  7-a.trty  r£<x.y&. 

26 


FIG.  52.—  Coefficient  of  electric  dissipation. 

FIG.  54.  —  Comparison  of  the  diurnal  periods  of  the  temperature-fall, 
pressure,  temperature,  vapor  tension,  electric  potential,  and  coefficient 
of  dissipation. 

sSumrne? 

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JSarth   ag  chct?~gred!  trz&i  neyafev-e  torts 

97 


IV.— THE  DIURNAL  PERIODS  OF  THE  TERRESTRIAL  MAGNETIC  FIELD  AND  THE  APERIODIC  DISTURBANCES. 


THE  DIURNAL  VARIATIONS  OF  THE  TERRESTRIAL  MAGNETIC  FIELD, 

In  the  years  1889-1891  I  computed  a  series  of  hourly  mag- 
netic deflecting  vectors  for  30  stations,  in  polar  coordinates, 
.f  =  total  vector,  a  =  the  horizontal  component,  a  =  the  angu- 
lar altitude  positive  above  the  horizon,  ,3  =  azimuthal  angle 
counted  from  the  north  point  of  the  magnetic  meridian 
through  the  west  =  90°,  south  =  180°,  east  =  270°.  These 
were  derived  from  the  rectangular  variations,  J  H  horizontal 
force  positive  northward,  J  D  declination  positive  westward, 
J  T~  positive  zenithward,  by  means  of  a  simple  scale  diagram 
containing  polar  and  rectangular  coordinate  systems  at  the 
same  center.  This  presentation  of  the  available  data  of  obser- 
vation included  the  diurnal  variation  of  the  magnetic  field, 
and  also  the  variation  from  day  to  day  eliminating  the  hourly 
periodicity.  The  resulting  tables  are  bulky  and  there  has 
been  no  opportunity  to  publish  them  in  extenso,  but  brief 
summaries  of  the  subject  matter  have  appeared  in  several 
places1.  This  work  has  aroused  some  critical  discussion,  but  for 
the  greater  part  of  an  academic  character  which  threw  little 
additional  information  upon  the  solution  of  the  numerous  dif- 
cult  problems  in  solar  physics  and  cosmical  meteorology  that 
are  involved.  It  is  quite  evident  that  the  authors  of  the  com- 
ments did  not  always  have  in  mind  the  details  or  the  minor 
facts  which  must  be  accounted  for  in  a  final  solution.  It  is 
easy  to  propose  a  vague  general  theory,  but  to  bring  it  down 
to  exact  harmony  with  the  many  special  peculiarities  of  the 
varying  magnetic  field  is  no  easy  problem  to  resolve. 

In  1889  Schuster1  published  his  solution  for  the  diurnal 
variation  of  the  vertical  force  derived  from  four  stations,  and 
ascribed  to  the  assumed  counterpart  electric  currents  to  a 
sensitive  state  of  the  upper  atmosphere.  In  1897  von  Bezold* 
further  discussed  the  subject  as  a  continuation  of  the  same 
data.  In  1902  H.  Fritsche  *  computed  the  variations  from 
the  difference  data,  J  H,  J  D,  J  V,  by  means  of  Gaussian  coef- 
ficients, and  likewise  attributed  the  magnetic  effects  to  sup- 
posed electric  currents  in  the  upper  atmosphere.  In  his 
paper  of  1903,  Adolph  Schmidt5  has  adopted  the  method  of 
deflecting  vectors,  and  in  his  other  papers  seems  to  favor  an 
electric  current  system  in  the  high  strata.  Also,  A.  S.  Steen6 
has  worked  out  an  elaborate  system  of  upper  air  electric  cur- 
rents to  account  for  the  diurnal  variation  of  the  magnetic  field. 

Other  writers,  W.  Sutherland,  A.  Nippoldt,  W.  van  Bemme- 
len,  J.  Liznar,  Carlheim-Gyllenskiold,  Ch.  Chree,  and  L.  A. 
Bauer  seem  to  favor  a  solution  of  the  same  character. 

I  must  confess  that,  aside  from  the  entirely  vague  nature  of 
this  hvpothesis,  I  have  never  been  able  to  concede  that  it 

1  Weather  Bureau  Bulletin  No.  2,  1892.  Astrophysical  Journal,  Octo- 
ber, 1893.  American  Journal  of  Science,  December,  1894,  August,  1895. 
Weather  Bureau  Bulletin  No.  21,  1898.  Weather  Bureau  Annual  Eeport, 
1898-99,  chapter  9.  Eclipse  Meteorology  and  Allied  Problems,  1902, 
chapter  4. 

'The  Diurnal  Variation  of  Terrestrial  Magnetism.     A.  Schuster,  1889. 

*Zur  Theorie  des  Erdmagnetismus.     W.  von  Bezold,  1897. 

4  Die  Tagliche  periode  der  Erdmagnetischen  Elemente.  H.  Fritsche, 
1902. 

5Eine  Sammlung  der  wichtigsten  Ergebnisse  erdmagnetischer  Beo- 
bachtungen.  A.  Schmidt,  1903. 

6  The  Diurnal  Variation  of  Terrestrial  Magnetism.     A.  S.  Steen,'1904. 


contains  the  true  germ  of  the  solution  of  the  problem.  That 
theory  has  received  much  additional  popularity  from  the  sup- 
posed bombardment  of  the  upper  strata  of  the  earth's  atmos- 
phere by  the  ions  ejected  from  the  solar  surface  and  trans- 
ported to  the  region  of  the  earth's  orbit  by  the  mechanical 
pressure  of  light,  which  were  described  as  thereupon  induc- 
ing the  required  electric  currents.  It  was  quite  impossible  to 
understand  how  such  a  general  action  of  currents  in  the  upper 
strata  could  produce  the  strongly  localized  effects  observed 
at  the  surface  of  the  earth,  which  so  persistently  follow  the 
meteorological  elements  both  diurnally  and  annually.  I  have, 
accordingly,  (1)  argued  against  the  efficiency  of  these  hypo- 
thetical upper  strata  electric  currents  to  produce  the  details 
noted  in  the  magnetic  field,  and  I  have  (2)  endeavored  to  show 
that  the  general  motions  of  the  atmosphere  and  the  cyclonic 
and  anticyclonic  actions  can  not  account  for  the  observed 
phenomena,  taken  the  world  over,  as  shown  by  my  30-inch 
globe  model  of  1893. 

It  is  true  that  my  own  working  hypothesis  was  not  complete 
even  in  my  own  mind,  and  I  have  supposed  there  are  steps  in 
the  series  of  causes  and  effects  that  still  require  to  be  added. 
My  view  was  simply  this,  that  the  sun's  electromagnetic  or 
radiant  field  of  energy  falling  upon  the  atomic  and  molecular 
constituents  of  the  earth's  atmosphere  transformed  them  into 
temporary  magnetic  states,  by  polarizing  some  of  them  in  situ, 
that  is,  throughout  the  strata  traversed  by  the  solar  energy. 
These  temporary  magnets  produced  a  quasi  magnetic  field 
which  deflected  the  normal  field  as  observed.  The  deflecting 
forces  were  the  products  of  the  physical  processes  involved  in 
this  action  of  the  radiation  upon  the  atoms  and  molecules  of 
the  atmosphere.  This  theory  was  constructed  before  the 
phenomenon  of  ionization  of  the  constituents  of  the  terres- 
trial atmosphere  by  solar  radiation  had  been  discovered,  and, 
of  course,  there  was  little  scientific  material  to  justify  my  hypo- 
thesis at  that  time.  Furthermore,  after  the  discovery  of  the 
existence  of  positive  ( +)  ions  and  negative  ( — )  ions  as  constit- 
uents of  the  atmosphere  had  been  made,  it  still  remained  im- 
possible to  match  the  computed  magnetic  deflecting  forces  with 
the  pressure  and  temperature  period  of  diurnal  variation  as  ob- 
served at  the  surface  of  the  earth.  The  search  for  conclusive 
evidence  of  the  synchronism  of  magnetic  vectors  and  surface 
temperatures  and  pressures  was  always  unsuccessful,  but, 
fortunately,  this  defect  now  seems  to  have  been  overcome  by 
the  results  of  the  computations  summarized  in  this  present 
series  of  papers  upon  diurnal  pressure  and  temperature  waves 
in  the  free  air  above  the  surface  within  one  mile  of  the  ground. 
The  desired  synchronism  seems  to  be  so  perfect  as  to  leave 
little  ground  for  further  doubt  that  the  diurnal  variation  of  the 
earth's  magnetic  field  is  due  to  the  movement  of  the  positive 
(  +  )  ions  of  electricity  in  the  lower  strata  of  the  atmosphere  in 
streams  that  are  induced  and  controlled  chiefly  by  the  diurnal 
temperature  waves  that  prevail  in  the  lowest  strata.  I  shall, 
accordingly,  consider  this  paper  as  a  supplement  to  chapter  4 
of  Bulletin  No.  21.  The  description  of  the  magnetic  vectors 
there  given  is  correct  and  in  agreement  with  the  systems 
derived  by  later  computers,  but  the  process  of  producing 
them,  as  now  understood,  is  in  accordance  with  the  facts 
that  have  been  worked  out  since  that  paper  was  written. 

29 


30 


THE  DIURNAL  MAGNETIC  VECTOES  AS  THE  EFFECT  OF  THE  DIUENAL  TEM- 
PEBATUBE  WAVES  UPON  THE  EEDISTRIBUTION  OF  THE  POSITIVE  IONS 
IN  THE  LOWEE  STRATA  OF  THE  ATMOSPHEEE. 

This  subject  can  be  best  presented  to  the  reader  by  making 
a  compilation  of  the  vectors  of  the  diurnal  deflecting  magnetic 
forces  and  as  computed  for  the  same  latitudes  as  those  repre- 
sented by  the  meteorological  stations  that  have  been  used  in  the 
comparison.  For  this  purpose  the  following  five  stations  have 
been  selected,  as  they  are  located  in  the  North  Temperate  Zone, 
but  in  widely  distributed  longitudes :  Washington,  Paris,  Vi- 
enna, Tiflis,  and  Zi-ka-wei.  Properly,  Zi-ka-wei  belongs  part- 
ly to  the  Temperate  Zone  belt  and  partly  to  the  Tropic  Zone 
belt,  magnetically  considered,  because  it  is  so  far  from  the 
north  magnetic  pole  as  to  be  immersed  in  the  tropical  influence 
during  several  months.  Although  this  affects  the  azimuth  of 
the  hours  during  the  night,  I  have  not  removed  it  from  the 
group  of  stations.  The  computed  values  of  s,  a,  /?  are  extracted 
from  the  tables  described  in  chapter  4,  of  Bulletin  No.  21,  and 
an  example  is  given  in  full  for  the  months  of  February  and 
August  in  Table  10,  "Hourly  values  of  the  polar  coordinates, 
s,  a,  ,9,  at  five  stations  in  the  North  Temperate  Zone  ".  The 
mean  values  were  computed  for  each  element  at  every  hour, 
and  these  are  given  for  each  month  in  Table  2,  "Vectors  of  the 
diurnal  magnetic  deflecting  forces",  s  is  in  units  of  the  fifth 
decimal  or  0.00001  of  the  unit  of  the  C.  6r.  S.  system;  a  =  the 
altitude  angle  positive  above  the  horizon;  /9  =  the  azimuth 
angle  counted  from  the  north  through  the  west. 

It  is  difficult  to  exhibit  the  results  of  the  Tables  10  and  11 
on  a  diagram  of  only  two  dimensions,  and  I  have  made  use  in 
my  studies  of  globe  models  constructed  of  rubber  balls  with 
pins  for  vectors,  or  else  the  large  30-inch  globe  model  already 
mentioned.  However,  a  drawing  has  been  made  in  fig.  55, 
"  Diurnal  variation  of  the  magnetic  vectors  s,  a,  ft  for  latitudes 
+  30°  to  +60°".  The  vector  length  s  and  the  vertical  angle  a 
are  plotted  for  each  month,  and  the  direction  in  azimuth'  ft  is 
laid  down  only  for  January  and  July,  as  the  variation  in  this 
element  is  not  very  great  in  the  course  of  the  year.  We  should, 
therefore,  interpret  the  vectors  as  follows:  The  vector  (s,  a) 
should  be  understood  to  stand  in  the  plane  of  the  azimuth  /?, 
and  make  with  it  the  angle  a  which  is  here  given.  Generally, 
the  vectors  from  8  a.  m.  to  7  p.  m.  are  directed  toward  the 
south,  and  those  from  8  p.  m.  to  7  a.  m.  toward  the  north. 
As  my  purpose  is  to  consider  chiefly  the  relation  of  the  streams 
of  +  ions  in  the  air  to  the  vector  (s,  a)  I  have  practically  sacri- 
ficed the  azimuth  in  the  diagram.  On  the  globe  model  the 
entire  system  is  clearly  displayed  and  it  should  be  studied  in 
that  way. 

On  fig.  55  there  are  seen  to  be  four  critical  points  in  the 
distribution  of  the  diurnal  vectors: 

( 1 )  The  first  point  marks  a  sudden  increase  in  the  value  of 
the  deflecting  force  s  up  to  a  maximum,  and  it  occurs  in  the 
forenoon,  ranging  from  about  8  a.  m.  in  winter  to  6  a.  m.  in  the 
summer.     This  is  the  hour  at  which  the  azimuth  (3  shifts  from 
the  northern   to  the  southern   quadrants.     About  two  hours 
later  the  vertical  angle  a  passes  through  0°  so  that  the  vector 
changes  from  below  to  above  the  horizon. 

(2)  The  second  point  occurs  at  11-12  a.  m.  in  winter  and 
10-11  a.  m.  in  summer,  where  the  azimuth  p  shifts  from  east 
to  west  through  the  south,  this  being  the  well-known  reversal 
of  the  needle  before  noon.     The  value  of  s  at  this  point  is  at 
a  slight  minimum  relative  to  its  values  earlier  and  later;  this 
midday  minimum  appears  in  nearly  every  month  of  the  com- 
putation, but  especially  in  summer. 

(3)  The  third  point  occurs  after  the  true  midday  maximum 
of  s,  about  3  p.  m.,  where  the  vector  (s,  a)  changes  from  above 
to   below  the   horizon,  and  a  passes  again   through   the  zero 
value  of  the  angle.     This  point  changes  from  about  2  p.  m.  in 
winter  to  4  p.  m.  in  summer,  thus  moving  in  the  opposite  direc- 
tion from  midday  to  that  indicated  in  the  forenoon  vectors. 


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FIG.  56.— The  annual  variation  of  the  surface  temperature  at  Blue  Hill. 

(4)  The  fourth  point  is  where  the  azimuth  ;9  shifts  from  the 
first  and  second  quadrants  to  the  third  and  fourth,  and  it 
occurs  at  about  6-7  p.  m.  in  winter,  but  at  7-8  p.  m.  in  the 
summer,  at  the  time  of  the  setting  of  the  sun.  On  fig.  55 
these  four  special  points  in  the  system  of  diurnal  vectors  are 
indicated  by  the  four  lines  marked  (1),  (2),  (3),  (4),  and  by 


31 


their  course  they  show  that  the  entire  action  which  produces 
this  magnetic  disturbance  of  the  normal  field,  contracts  in 
time  toward  noon  in  the  winter,  and  spreads  away  from  it  in 
the  summer.  This  remarkable  change  in  the  location  of  the 
turning  points  is  related  without  doubt  to  a  similar  change  in 
the  diurnal  distribution  of  the  temperature  in  the  lower  strata 
of  the  atmosphere,  which  must  be  closely  associated  with  the 
magnetic  variations. 

Tn  order  to  show  how  exactly  these  two  phenomena  syn- 
chronize in  time  during  the  course  of  the  year,  I  have  trans- 
ferred to  fig.  56  from  figs.  14-25  the  surface  temperatures  as 
observed  at  Blue  Hill,  plotting  them  in  the  sense  indicated  by 
the  coordinate  values.  If  the  line  (1)  is  drawn  at  the  locus  of  the 
first  active  rise  of  temperature,  at  about  two  hours  later  than 
the  minimum,  the  course  is  marked  at  an  earlier  hour  in  sum- 
mer than  in  winter.  The  line  (2)  is  drawn  at  about  halfway 
up  the  forenoon  temperature  slope;  line  (3)  at  the  maximum 
of  the  temperature,  and  line  (4)  at  about  halfway  down  the 
afternoon  temperature  slope.  On  comparing  the  lines  (1),  (2), 
(3),  (4)  of  fig.  56  with  those  of  fig.  55,  it  is  observed  that  the 
annual  curvature  of  the  lines  is  generally  so  much  in  agree- 
ment as  to  make  it  very  probable  that  the  magnetic  field  and 
the  temperature  are  both  direct  effects  of  the  solar  radiation, 
which  itself  has  an  entirely  similar  course  to  these  in  the 
North  Temperate  Zone.  Now,  since  it  is  well  known  that  this 
diurnal  temperature  effect  is  confined  to  the  lower  strata  of 
the  atmosphere,  within  two  miles  of  the  surface,  I  have  been 
unable  to  concede  that  the  diurnal  magnetic  variations  can  be 
caused  by  electric  currents  in  the  upper  strata  of  the  atmos- 
phere, as  assumed  by  Professor  Schuster  and  other  magneti- 
cians,  or  that  it  can  be  caused  by  a  bombardment  of  the  upper 
strata  by  the  ions  transported  in  the  solar  radiation,  as  sup- 
posed by  Professor  Arrhenius  and  other  physicists.  While  I 
have  been  unable  to  relinquish  my  belief  in  a  cause  located  in 
the  lower  strata  of  the  atmosphere,  it  has  been  an  exceedingly 
difficult  thing  to  discover  a  substantial  physical  cause  that 
will  fix  the  exact  location  of  a  system  of  electric  currents,  or 
other  source  of  these  magnetic  vectors,  in  this  region,  and, 
indeed,  I  had  not  been  able  to  do  so  before  arriving  at  the 
results  of  the  kite  observations  as  exhibited  in  the  preceding 
papers  of  this  series.  We  have  been  led,  at  length,  very  natu- 
rally to  see  in  the  movement  of  the  positive  (-)-)  ions  in 
streams,  whose  directions  are  determined  by  the  temperature 
distributions  in  the  lower  strata,  a  sufficient  cause  for  the 
diurnal  variation  of  the  electric  potential  field,  and  I  shall  now 
show  that  this  cause  also  accounts  equally  well  for  the  diurnal 
variation  of  the  magnetic  field  in  the  North  Temperate  Zone. 

The  general  relations  may  be  represented  schematically  by 
fig.  57,  "The  probable  relations  between  the  temperature  waves, 
the  streams  of  positive  (  +  )  ions,  and  the  magnetic  vectors  in 
the  lower  strata  of  the  atmosphere".  Let  A  represent  the  sur- 
face of  the  earth  which  is  charged  with  negative  electricity. 
A  portion  of  this  charge  is  derived  from  the  ionized  contents 
of  the  atmosphere,  due  to  the  action  of  the  short  waves  of  the 
solar  radiation  upon  the  constituents  of  the  atmosphere,  espe- 
cially the  aqueous  vapor  located  within  an  arch  spanning  the 
Tropics.  Another  portion  of  the  negative  charge  is  probably 
derived  from  inside  the  earth,  and  is  due  to  the  excess  of  dif- 
ferential circulation  of  the  negative  ( — )  ions  over  the  positive 
(  + )  ions  in  the  atomic  conflict  at  the  prevailing  high  temper- 
ature and  pressure,  by  which  more  of  the  negative  electric 
ions  are  detached  from  the  atoms  and  in  circulating  are  polar- 
ized by  the  earth's  rotation  so  as  to  produce  the  internal  mag- 
netism of  the  earth  and  an  electrostatic  charge  at  the  surface. 
If  the  negative  ions  rotate  more  rapidly  than  the  positive,  as 
with  the  velocity  of  light,  the  deflecting  force  due  to  the  earth's 
rotation  must  be  large,  and  tend  to  cause  these  ions  to  move 
in  planes  perpendicular  to  the  axis  of  rotation.  This  will  cause 
an  internal  magnetic  field  directed  from  north  to  south. 


The  surface  charge  of  negative  ions  is  supposed  to  rest  quite 
steadily  on  the  earth,  or  within  it,  while  the  positive  (  +  )  ions 
of  the  atmosphere  rise  and  fall  from  one  stratum  to  another  ac- 
cording to  the  change  in  the  air  temperatures,  as  if  the  posi- 
tive ( + )  ions  had  an  affinity  for  certain  temperatures,  which 
they  seek  through  vertical  and  horizontal  motions.  Let  B 
represent  the  ordinary  surface  temperature  wave,  with  which 
it  has  never  been  possible  to  associate  the  diurnal  magnetic 
vectors.  Let  G  represent  the  semidiurnal  temperature  wave 
in  the  lower  strata  of  the  atmosphere  as  integrated  in  the  di- 
urnal convections,  generally  within  half  a  mile  of  the  ground. 
The  maximum  temperature  occurs  at  3  a.  m.  and  3  p.  m.,  and 
the  minimum  at  8  a.  m.  and  8  p.  m.,  both  of  these  subject  to 
the  annual  variation  in  time  already  indicated.  Let  D  repre- 
sent the  probable  streams  of 'positive  ions,  directed  vertically 
upward  at  3  a.  m.  and  3  p.  m.,  but  downward  at  8  a.  m.  and  8 
p.  m.  It  should  be  observed  that  at  3  a.  m.  the  vertical  up- 
ward current  of  the  semidiurnal  wave  is  really  neutralized  by 
the  downward  current  of  the  surface  wave,  and  that  during 
the  night  hours  we  should  have  small  residual  motions  on  the 
whole  of  a  downward  direction;  that,  at  8  a.  m.  and  8  p.  m. 
the  downward  semidiurnal  waves  prevail  because  the  surface 
temperatures  are  nearly  normal  to  the  day  and  the  convectional 
currents  are  producing  lower  temperatures;  and,  that,  at  3 
p.  m.  both  the  diurnal  and  the  semidiurnal  waves  unite  in  a  com- 
mon upward  vertical  component.  We  may  assume,  then,  that 
the  positive  ions  descend  vertically  at  8  a.  m.  and  8  p.  m.,  but 
ascend  vertically  at  3  p.  rn.  The  accompanying  adjacent 
streams  on  the  preceding  side  of  the  8  a.  m.  vertical,  bend  to  the 
left  in  the  early  morning  hours,  but  to  the  right  after  that  hour. 
These  latter  naturally  recurve,  becoming  horizontal  at  10 
a.  m.  to  11  a.  m.  in  order  to  ascend  in  the  warm  midday  current. 
At  8  p.  m.  the  positive  (-f )  ions  first  descend,  recurve  by  be- 
coming horizontal  at  6  p.  m.  to  7  p.  m.  and  ascend  in  the  warm 
afternoon  current,  while  those  farther  to  the  right  slowly 
descend  throughout  the  night.  Let  E  represent  the  corres- 
ponding magnetic  deflecting  forces,  which  are  generally  found 
to  be  at  right-angles  to  the  electric  streams  as  thus  located 
and  always  directed  in  the  same  sense. 


JElectric 
current. 


vector. 


This  remarkably  consistent  correlation  of  cause  and  effect 
throughout  the  diurnal  fields  is  greatly  in  favor  of  the  theory 
here  described.  Finally,  it  should  be  remembered  that  this  entire 
temperature  system  is  moving  as  indicated  by  the  arrow  F  on 
the  diagram  from  right  to  left,  and  that  the  warm  wave  is  con- 
tinuously intruding  upon  the  cool  regions  to  the  left  of  it. 
If  the  positive  (  +  )  ions  seek  to  avoid  an  excess  of  warm  tem- 
perature by  streaming  from  low  levels  during  the  hours  from 
10-11  a.  m.  to  6-7  p.  m.  into  the  higher  levels  with  a  maxi- 
mum at  3  p.  m.,  that  is  generally  by  moving  upward  in  the 
warm  current,  the  effect  is  to  leave  the  positive  (-f-)ions  in 
the  higher  strata  throughout  the  evening  and  night  hours. 
There  is  not  so  much  a  continuous  electric  circuit,  with  the 
same  velocity  in  all  parts  of  it  as  in  a  conductor,  but  rather  an 
alternate  rise  and  fall  of  the  electric  charges  at  different  parts 
of  the  day,  that  is  a  falling  by  night  and  a  rising  by  day, 
somewhat  as  is  indicated  in  the  diagrams.  The  westward 
lateral  movement  of  the  diurnal  system  probably  tends  to  keep 


32 


wider  open  the  streams  of  ions  before  noon,  at  10  a.  m.  to  1 
p.  m.,  and  to  make  them  closer  together  at  about  6  p.  m.  to  7 
p.  m.  At  the  same  time,  as  already  explained,  there  is  pro- 
duced the  increase  of  the  atmospheric  electric  potential 
gradient  to  a  maximum  at  8  a.  m.  and  8  p.  m.  by  the  approach 
of  the  positive  ( + )  ions  to  the  negative  ( — )  ions  lying  at  the 
surface,  also,  an  increase  in  the  rate  of  dissipation  of  the  two 
kinds  of  charges  by  the  more  immediate  mixture  and  contact. 
It  is  not  necessary  to  remark  that  we  do  not  suppose  that  the 
positive  ( -f )  ions  and  the  negative  ( — )  ions  are  separated 
from  each  other  so  exclusively  as  is  here  indicated,  but  only 
that  there  is  an  excess  of  the  positive  (  +  )  ions  in  the  strata 
above  the  ground,  and  an  excess  of  the  negative  ( — )  ions 
near  the  surface.  It  may  be  noted  that  the  conflict  in  direc- 
tion from  4  p.  m.  to  9  p.  m.  between  the  convection  air  cur- 
rents and  between  the  streams  of  the  ions,  one  being  upward 
and  the  other  downward,  is  very  favorable  to  the  production 
of  thunderstorms. 

THE  DIBHNAL  MAGNETIC   VECTOES    IN  THE    POLAR,   TEMPERATE,  AND 
TROPICAL  ZONES  OF  THE  EARTH. 

Similar  considerations  applied  to  the  magnetic  hourly  vec- 
tors which  have  been  computed  in  the  other  zones  of  the 
earth,  and  described  in  chapter  4  of  Bulletin  No.  21,  lead  to 
the  following  conclusions,  illustrated  schematically  in  fig.  58. 
The  normal  magnetic  field  of  the  earth,  positive  in  the  South- 
ern Hemisphere,  has  the  horizontal  component  directed  north- 
ward, while  the  vertical  is  upward  in  the  Southern  Hemisphere, 
but  downward  in  the  Northern  Hemisphere.  The  downward 
positive  (  +  )  ion  stream  repels  the  north  end  of  the  magnet 
eastward  in  the  North  Temperate  Zone,  but  westward  in  the 
South  Temperate  Zone;  the  upward  positive  (-f)  ion  stream 
works  in  the  opposite  sense.  Hence,  the  descending  positive  ( + ) 
ion  stream  from  7  p.  m.  to  11  a.  m.  (fig.  57)  in  the  Northern  Hem- 
isphere directs  the  north  end  of  the  needle  eastward,  but  in  the 
Southern  Hemisphere,  westward.  The  ascending  stream  di- 
rects it  westward  in  the  Northern  Hemisphere  and  eastward  in 
the  Southern  Hemisphere.  The  same  diurnal  temperature 
waves,  therefore,  produce  the  required  opposite  magnetic 
effect  in  the  respective  hemispheres.  In  the  Tropical  Zone  the 
vectors  on  the  sunward  side  are  directed  northward  for  the 
ascending  positive  (-)-)  ion  streams,  and  southward  in  the 
night,  4  p.  m.  to  8  a.  m.  for  the  descending  streams.  In  the 
Polar  Zone  the  outspreading  magnetic  sheets  on  the  morning 
side  of  the  pole  imply  a  descending  stream  of  ions  which  is 
directed  from  left  to  right,  or  west  to  east;  and  on  the  afternoon 
side  the  ascending  and  concentrating  magnetic  vector  sheets 
imply  an  outflowing  system  of  positive  ( + )  ions  which  ascend 
into  regions  about  the  surface.  Generally,  these  magnetic 
vectors  in  the  three  zones  require  electric  currents  directed 
from  west  to  east  in  the  Polar  Zone  athwart  the  direction  of 
the  lines  of  the  solar  radiation;  those  in  the  Temperate  Zones 
require  lines  nearly  in  planes  from  north  to  south,  and  also 
athwart  the  solar  radiation  field;  finally  those  in  the  Tropics 
require  positive  (  +  )  ion  streams  parallel  to  the  direction  of 
the  same  radiation.  These  three  rectangular  systems  of  elec- 
tric currents  evidently  form  those  types  of  couples,  exactly 
the  counterparts  of  the  three  sets  of  magnetic  couples  which 
were  described  in  the  same  chapter  of  Bulletin  No.  21.  For 
some  reason  the  positive  (  +  )  ions  seem  to  prefer  to  travel  at 
right  angles  or  else  parallel  to  the  lines  of  the  electromagnetic 
radiation,  even  when  they  are  passing  along  paths  which  are 
rendered  favorable  by  the  temperature  conditions  already 
existing  in  the  lower  strata  of  the  atmosphere.  It  is  evident 
that  these  prevailing  conditions  imply  a  possible  solution  of 
several  important  physical  questions  in  electricity  and  mag- 
netism in  the  earth's  atmosphere,  when  suitable  observations 
have  been  acquired.  The  theory  which  I  advanced  to  account 
for  the  observed  diurnal  magnetic  vectors  in  my  preliminary 
papers  is  now  much  more  satisfactorily  stated,  by  such  an 


addition  to  its  terms  as  has  been  drawn  from  the  process 
depending  upon  the  ionization  and  temperature  effects  of 
the  solar  radiation  in  the  lower  atmosphere.  Apart  from 
clearness  of  exposition,  it  seems  to  me  that  the  view  there  ad- 
vanced, namely,  that  the  magnetic  vectors  are  products  of  the 
electromagnetic  radiation  as  the  result  of  its  action  on  the 
atoms  of  the  atmosphere  is  substantially  strengthened.  The 
entire  subject,  though  intellectually  more  satisfactory,  is  also 
much  more  difficult  to  handle  scientifically,  because  the  inter- 
mediate steps  involved  in  the  action  of  the  ions  in  relation  to 
the  temperature,  must  be  worked  out  by  observations  in  the 
lower  strata  of  the  atmosphere,  and  such  data  are  very  difficult 
to  acquire  in  a  reliable  form. 

THE  SYSTEM  OF  DAILY  MAGNETIC  VECTORS,  AS    DISTINCT   FROM  THE 
HOURLY  VECTORS. 

Besides  the  system  of  hourly  deflecting  magnetic  forces 
described  in  chapter  4,  Bulletin  No.  21,  I  also  worked  out  a 
second  vector  system,  which  gives  the  vectors  day  by  day, 
disturbing  the  normal  magnetic  field  in  the  day  intervals, 
taking  the  several  successive  groups  of  24  hours  in  succes- 
sion. These  vectors  are  summarized  in  chapter  3,  of  the 
same  bulletin,  and  it  was  there  shown  that  they  consist  of 
vectors  acting  nearly  in  the  planes  of  the  magnetic  meridians 
directed  northward  or  southward  as  the  case  may  be.  Since 
the  entire  magnetic  field  of  the  earth  is  involved  in  these  dis- 
turbances, which  often  run  three  or  four  days  in  the  same 
direction,  before  reversal  to  the  other  side  of  the  normal  oc- 
curs, it  is  necessary  to  seek  for  a  general  cause  instead  of  one 
that  is  distinctly  local.  The  mere  temperature  effects  of 
meteorological  circulation  can  not  be  the  dominant  cause,  be- 
cause the  two  systems  of  conditions  do  not  synchronize.  It 
was  also  shown  that  this  general  magnetic  field,  taking  the 
annual  values  of  the  vector  s,  does  vary  in  parallel  with  that 
of  the  solar  field  as  shown  by  the  frequent  number  of  spots, 
faculae,  and  prominences.  According  to  that  interpretation  of 
several  phenomena  which  was  adopted  and  which  is  probably 
physically  correct,  the  sun  was  found  to  be  magnetized. 
The  solar  action  and  the  magnetic  terrestrial  effect  undoubt- 
edly synchronize  in  the  long  run,  but  there  has  been  great 
difficulty  in  assigning  so  large  physical  fluctuations  to  the 
sun  itself  as  seem  to  be  required  to  account  for  the  observed 
magnetic  conditions  at  the  earth.  It  has  seemed  to  me  nec- 
essary to  assign  to  the  direct  magnetic  field  of  the  sun  at 
least  the  function  of  setting  in  operation  such  terrestrial  forces 
in  the  earth's  atmosphere  as  should  make  up  between  them 
the  required  magnetic  efficiency.  Just  what  that  terrestrial 
process  is  in  fact,  there  has  been  trouble  in  detecting,  and  in 
assigning  to  it  a  sufficiently  natural  modus  operandi.  The  vio- 
lent fluctuations  of  the  magnetic  field  could  hardly  be  ascribed 
exclusively  to  variations  in  the  normal  solar  electromagnetic 
radiations,  for  two  reasons:  (1)  The  sun  would  be  a  variable 
star  of  such  a  convulsive  type  as  to  be  inconsistent  with  the 
comparatively  steady  flow  of  heat  which  the  earth  receives 
from  it.  Nor  can  this  view  be  suitably  modified  by  adding 
such  a  bombardment  of  solar  ions  as  Arrhenius  has  suggested, 
because  their  possible  efficiency  is  not  nearly  great  enough  to 
match  the  great  magnetic  fluctuations  which  are  continually 
being  recorded.  (2)  The  vector  system  pertaining  to  these 
daily  disturbances  is  entirely  different  in  type  from  that 
found  in  the  hourly  variations.  Indeed,  I  showed  by  the 
computation  on  Table  15,  page  76,  Bulletin  No.  21,  that  in  the 
case  of  strong  disturbances  the  ordinary  hourly  disturbing 
vectors  (fig.  58)  are  transformed  hour  by  hour  into  a  system 
of  vectors  like  the  general  type  (fig.  59),  thus  proving  that 
these  two  phenomena  have  essentially  different  originating 
causes,  so  far  as  their  effects  on  the  observed  magnetic  vectors 
are  concerned.  I  have  not  failed  to  recognize  the  difficulties 
of  my  own  theories  in  this  problem,  nor  have  I  discovered  in 
other  papers  a  solution  which  seemed  in  anywise  competent 


Plate  I. 


33 


Worth. 


West,. 


South. 

FIG.  58. — The  streams  of  +  ions  causing  the  diurnal  magnetic  vectors  in 
the  Polar,  Temperate,  and  Tropical  zones  of  the  earth. 


FIG.  59,— The  general  disturbance :  Magnetic  vectors  directed  south- 
ward and  caused  by  a  flow  of  +  ions  from  south  to  north  in  the  air. 


FIG.  55. — Diurnal  variation  of  the  magnetic  vectors,    s,  a,  j3,  for  latitudes 
+  30°  to  +  60°;  K,  a,  for  each  month,  [),  for  January  and  July. 


Plate  II. 


34 


Midn.l      23      436      7     8     &     10     11  Noon  J      23456789     10     HMidn. 


FIG.  57. — Probable  relations  between  the  temperature  waves,  the  streams 
of  +  ions,  and  the  magnetic  vectors  in  the  lower  strata  of  the  atmos- 
phere. 

A  —  negatively  charged  surface  of  earth. 
B  zz  the  surface  temperature  wave. 


C  =  the  semidiurnal  temperature  wave  at  the  height  of  400-600  meters. 
D  —  the  probable  stream  lines  of  the  positive  ions,  as  moving  charges. 
E  —  the  corresponding  magnetic  vectors. 
F  =:  direction  of  motion  of  the  system. 


35 


to  account  for  all  the  conditions  at  the  solar  end  and  at  the 
terrestrial  end  of  the  line  of  cause  and  effect.  The  following 
view  is,  therefore,  suggested  with  the  impression  that  it  forms 
an  excellent  working  hypothesis  for  further  examination. 

Taking  such  a  group  of  lines  of  force  as  are  to  be  found  on 
charts  17,  18,  of  Bulletin  No.  21,  which  shows  that  the  mag- 
netic force  is  subject  to  world-wide  variations  of  the  same  type 
on  the  same  dates,  it  is  evident  that  the  normal  field  of  the 
entire  earth  is  for  a  while  disturbed  by  a  set  of  vectors  point- 
ing southward,  and  again  by  a  set  of  vectors  pointing  north- 
ward. The  mean  vectors  of  this  system  at  the  several  latitudes 
of  the  earth  were  computed,  and  they  are  plotted  on  chart  10 
of  Bulletin  No.  21.  They  have  longer  vectors  in  the  polar  re- 
gions and  in  latitudes  20°  to  40°  than  in  the  latitudes  40°  to 
60°  and  0°  to  20°.  I  have  transferred  them  to  fig.  59,  which 
shows  the  magnetic  vectors  s  directed  southward  and  to  fig. 
60,  which  shows  them  pointing  northward,  of  course  referring 
to  two  seperate  occasions.  This  alternate  action,  or  reversal 
of  the  entire  system  of  magnetic  deflecting  forces,  is  the  phe- 
nomenon to  be  explained. 

By  extending  our  notion  of  streams  of  positive  ( -f )  ions 
moving  from  point  to  point  in  the  atmosphere,  we  have  merely 
to  suppose  that  on  certain  provocations  the  positive  (  +  )  ions 
move  from  one  hemisphere  to  the  other  in  the  atmosphere,  re- 
turning again  through  the  outer  shell  of  the  earth,  as  indicated 
on  the  diagrams.  For  a  southward  directed  magnetic  system, 
the  positive  (  +  )  ions  stream  from  the  Southern  Hemisphere 
along  the  arches  in  the  atmosphere  most  favorable  to  their 
movement,  whether  due  to  temperature  and  vapor  conditions, 
or  to  special  ionization  and  conductivity  functions.  This  flow 
of  the  positive  ( +  )  ions  induces  the  magnetic  vectors  at  the 
surface,  and  the  positive  ( +  )  ions  stream  back  from  the  North- 
ern Hemisphere  to  the  Southern  through  the  crust  of  the 
earth,  thus  causing  the  earth  currents  which  always  accom- 
pany agitation  of  the  normal  magnetic  field.  For  a  northward 
directed  system  of  vectors  the  positive  (+)  ions  stream  from  the 
Northern  ito  the  Southern  Hemisphere  in  the  air,  and  return 
thence  through  the  outer  shell  of  the  earth.  The  magnitude 
of  the  disturbance  of  the  normal  magnetic  field  depends  upon 
the  intensity  of  the  stream  of  ions  flowing  along  these  paths, 
and  that  is  a  function  of  the  number  of  the  ions  and  the  veloc- 
ity of  their  motion, 


in  situ,  that  is  in  the  sun  itself,  as  for  example,  the  sun  spots, 
or  the  prominences,  is  attended  with  unusual  troubles  of  a 
physical  nature.  The  following  analysis  may  tend  to  throw 
some  light  on  the  subject. 

The  disturbances  which  occurred  at  Washington,  D.  C., 
during  the  years  1889,  1890,  and  1891  were  subjected  to  an 
analysis  similar  to  that  used  in  other  connections,  by  which  the 
polar  disturbance  vectors  a,  s,  a,  p,  were  computed  for  each 
half  hour  of  those  days  on  which  the  traces  were  decidedly 
agitated,  as  1889,  February  28,  29,  March  5,  6,  17,  and  so  on 
throughout  the  three  years.  The  purpose  was  to  fix  their 
daily  distribution  as  a  diurnal  period,  and  the  direction  from 
which  they  come  upon  the  normal  field.  The  mean  vector  for 
the  24  hours  was, 

s  =  245  for  ft  between  315°  and    45°  that  is  north ; 

315  "   ft        "         45°    "    315°       "       west; 

333  "   ft         "       135°    "    225°       "       south. 

308  "   ft         "       225°    "    315°       "       east. 

Hence,  the  south  quadrant  receives  the  strongest  impulse, 
while  the  east  and  west  quadrants  are  more  disturbed  than 
the  north  quadrant.  Fig.  61  contains  the  curve  of  relative 
numbers  showing  the  diurnal  frequency  of  the  disturbance, 
the  maxima  being  at  12  to  1  p.  m.  and  12  to  1  a.  m.  Compar- 
ing with  fig.  57,  it  is  seen  that  these  maxima  agree  with  the 
position  of  the  maxima  of  intensity  of  the  ascending  stream 
of  positive  (+)  ions,  as  determined  by  the  temperature  curve 
of  the  lower  strata,  that  is  the  one  located  a  few  hundred 
meters  above  the  surface.  We  may  infer  that  one  source  of 
the  magnetic  disturbances  is  in  the  temperature  waves  which 
induce  the  movement  of  the  streams  of  positive  (  +  )  ions, 
especially  in  a  vertical  direction.  Hence,  these  hourly  magnetic 
disturbances  are  specifically  meteorological  phenomena  occur- 
ing  in  the  lower  strata  of  the  atmosphere,  and  are  the  products 
of  the  solar  radiation  produced  through  the  intermediate 
agency  of  the  ionizatiou  and  temperature  waves. 


.  =  e    n    v 


+    + 


n_  v 


where  e  is  the  charge  of  electricity  of  each  ion,  n+  and  n_,  the 
number  of  the  positive  (-f-)  ions  and  the  negative  (  —  )  ions,  and 
v+  and  v_,  the  velocity  of  the  same.  The  simultaneous  occur- 
rence of  the  aurora  in  both  hemispheres  is  evidence  of  the  ac- 
tion of  the  ions  which,  in  traversing  the  gases  of  the  atmos- 
phere in  the  low  or  the  high  strata,  produce  the  observed 
luminous  effects  as  phosphorescence  or  fluorescence.  It  should 
be  observed  that  the  hourly  location  of  the  aurora  frequency 
occurs  in  the  regions  marked  out  on  fig.  58  by  the  streams  of 
iona,  that  is  in  the  earLy  morning  and  the  early  evening  hours, 
since  there  is  a  region  of  minimum  of  frequency  stretching 
from  11  a.  m.  across  the  polar  region  to  11  p.  m. 

This  simple  explanation  of  the  long  series  of  interrelated 
phenomena,  which  has  so  long  escaped  a  natural  correlation, 
has  much  to  commend  it  to  careful  consideration.  The  quan- 
titative determination  of  the  number  of  ions  involved,  and 
their  velocity  of  motion  in  the  circuit  from  one  hemisphere  to 
the  other,  will  require  much  exact  research  work  upon  the 
various  functions  involved  in  the  physical  processes. 

THE  DISTRIBUTION    OF    THE  APERIODIC    DISTURBANCES. 

It  has  been  very  difficult  to  assign  to  the  observed  disturb- 
ances of  the  magnetic  field,  that  is  to  the  large  variations  of  a 
spasmodic  character,  like  temporary  storms,  which  occur  in  the 
normal  field,  a  satisfactory  explanation.  The  attempt  to  ascribe 
the  physical  cause  exclusively  to  variations  of  the  solar  action 


rzA  i    titsfTtfron    rzri    Z3*sf7»9»rrrz 

eo 
so 
to 
30 
zo 

S 

> 

/ 

s 

/ 

/         \ 

\ 

r 

I 

1 

s 

•^ 

N, 

/ 

\ 

/ 

-?*• 

\ 

/ 

E    \ 

\ 

/ 

^ 

'  r 

/ 

FIG.  61. — Distribution  of  the  hourly  magnetic  disturbances  at  Wash- 
ington, D.  C.,  in  the  years  1889,  1890,  1891. 

There  is  yet  another  cause  for  the  other  type  of  great  mag- 
netic storms  which  endure  for  several  days,  as  distinct  from 
those  lasting  a  few  hours,  and  cause  the  excessive  variations 
in  the  diurnal  field.  In  working  up  my  data  into  the  26.68- 
day  period,  and  deducing  the  resulting  mean  magnetic  curve, 
as 'shown  on  chart  21,  Bulletin  No.  21,  or  by  the  upper  curve 
on  fig.  62,  I  excluded  the  large  magnetic  disturbances  be- 
yond a  certain  amplitude,  for  the  sake  of  obtaining  the  normal 
structural  magnetic  impulse  due  to  the  rotation  of  the  sun  on 
its  axis,  if  any  such  exists.  The  curve  mentioned  has  been 
found  to  reappear  generally,  though  at  the  expense  of  much 
waste  of  material  in  computing  to  eliminate  the  other  kinds  of 
irregularities  by  mutual  self  destruction,  in  nearly  all  the  solar 
and  terrestrial  phenomena.  It,  therefore,  seems  to  point  to  an 
organized  mass  in  the  sun  due  to  a  highly  viscous  mass  hav- 
ing great  rigidity  at  immense  pressure,  or  to  a  definite  organic 
circulation.  Similarly  I  have  counted  out  the  dates  of  occur- 
rences of  the  magnetic  disturbances  recorded  at  Greenwich, 
1882-1903,  as  collected  by  Mr.  Maunder  in  his  paper, 


Monthly  Notices  R  JL  SL  November,  1904,  and  entered  them 
in  a  tab^  based  upon  the  :^&S~dav  epbemeris.  The  result  is 
shown  aim  ia  fig.  63L  aad  it  MOM  to  imprj  that the  X,6B-day 
period  is  at  the  basis  of  the  distribution  of  the  great  magnetic 
storms,  rather  than  the  2*.3S-day  period,  which  is  the  average 
in  the  sun-spot  belt 


Jfumtrt' 
ItlUftlttH  ift 

fc_JL_J 


^^ 


¥2 


~ 


of  direct  magaaiJB  field,  is  passing  the  position  of  the  earth 
in  its  orbit  On -this  view  the  strain  is  removed  from  the  origi- 
nal theory  that  the  sun  can  not  by  direct  action  as  a  magnetic, 
sphere  influence  the  earth  to  the  full  extent  required  by  the 
observations,  because  only  a  part  of  the  energy  traverses  the 
eosmical  space  from  the  sun  to  the  earth,  while  the  remainder 
is  simply  due  to  the  nhraamn  of  ions  in  the  atmosphere  flowing 
as  adjustment  «f""i«iMff 

Fniiafh  ken  haea  shown,  I  believe,  to  make  it  clear,  (1)  that 
the  variations  of  the  terrestrial  magnetic  field  are  distinctly 
effects,  and  should  properly  be  examined  by 
rist  rather  than  by  the  geophysicist;  (8)  tha't 
of  the  electric,  magnetic,  and  temperature 


the 

:    - 


-  -: 


«£May period  ,M 


- 


In  Terrestrial  Magnetism,  YoL  X.  p.  12.  March,  1905,  Ch. 
Chrea  gires  a  table  which  shows  the  number  of  great  magnetic 
storms,  using  Maunder 's  data,  that  commeoced  on  the  several 
hours  of  the  day.  These  numbers  are  plotted  on  fig.  63  which 
•anaa  !••!  I  ha  i  ii  in  m  ilialiail  ••limum  •!  1  \i  m  The  num- 
bers are  distributed  without  dirtiantina  as  to  hours  *"if«ng 
the  night  aad  eailj  TBIH  aiag,  but  at  10  a.  m.  a  pronounced  in- 
crease in  the  number  par  hour  set  in  a  nine  culminates  aft 
1  p.  m.  and  falls  off  gradually  to  S  p.  m.  On  comparing  this 
curve,  fig.  63,  with  that  of  the  diurnal  disturbance  curre,  fig. 
61,  it  m  seem  that  the  principal  -""-»-  agree  at  the 
hour.  The  inference  is  that  the  gnat  disturbances 
several  days,  as  well  as  disturbances  which  are  limited  to  a  few 
hoars  in  duration,  each  toad  to  ciiatialiiUi  about  the  1  p.  m. 
hour  when  the  ascensional  current  of  the  puaitite  (-f-)  kms  is 
•Inmgial  T*inai  figs.  62  aad  63  it  is  quite  certain  that  the 
gnat  ilalailiaarni  have  two  fauna  *^^f™g  into  their  compo- 
sition, one  belonging  to  the  sun's  atmosphere  and  the  other  to 
the  earth's  ataMiayatnu-  The  final  solution  of  this  jaulifcia  is 
evidently  dependent  upon  a  knowledge  of  many  terms  irfanr 
than  a  mere  enumeration  and  matching  of  the  number  of  the 
sun  spots  aad  prominences  with  the 


efleula,  whether  at  the  sun  or  at  the  earth,  constitutes  one  of 
the  most  fascinating  problems  open  to  scientific  research.  If 
the  production  of  ions  by  solar  action,  their  distribution  stati- 
cally aad  dynamically  under  the  influence  of  atmospheric  pres- 
sure, temperature,  and  vapor  contents  can  be  thoroughly 
worked  out,  the  result  will  be  to  raise  meteorology  to  a  prac- 
tical science  of  the  highest  rank.  The  numerous  cross  con- 
between  radiation,  whether  variable  or  constant,  the 
ktion  in  the  solar  and  in  the  terrestrial  envelopes,  the 
circulation  of  the  solar  mass  and  of  the  earth's 
.  the  resulting  weather  and  «•««•»««*•»  make  up 


in  two  ways,  (1>  by  the  radial  path  o 
(1)  bj Recurved  path  of  a  direct ma| 
of  thece  may  operate  separately,  or 
to  alter  the  normal  balanci 
in  the  earth's  afakoapacre,  and  f 
paths  indicated  on  figa.  38, 59,  so 
>  ease  mav  be.     A»  a  matter  of 


.-_  '. 
. '  _.  -  r 


two  <•  lanmilij  q  are  found  to  i 
ing  vector  ijnlnai  pointing  southward,  so  tl 
(+)  ioae  low  northward  in  the  air  strata.  Th 
long  as  thei 


of  research  problems  of  much  difficulty,  and  yet  of  such 
promising  value  to  all  men  as  to  justify  a  much  greater  activ- 
ity on  the  part  of  astrophysicists  and  meteorologists  than  has 
been  t^iiiia  to  the  subject  of  eosmical  meteorology  in  the  past 

TH*  COOOOXKVKS  OT  THE  MTKXAI.  WESD  VZLOdTT. 

In  chapter  9,  of  the  International  Cloud  Report,  some  ac- 
count was  given  of  the  relation  between  the  distribution  of 
the  pressure  aaiua  aad  the  ••gaiilUi  field  •eutoui  in  the  polar 
veD  as  in  the  Tropics  and  middle  M*%nih-  It 
shown  that  the  diurnal  ware  in  the  Tropics  and  the  tem- 
perate zones  advances  over  the  earth  as  a  long  double  wave 
ertoadiap  from  latitudes  +60°  to  —CO0,  but  that  in  the  Polar 
Zone  a  single  wave  of  maximum  crosses  the  poles  with  a  phase 
about  90°  different  from  either  of  the  maximum  pressure 
waves  in  lower  latitudes-  It  appears  that  the  distribution  of 
the  magnetic  vectors  is  closely  associated  with  this  single 
wave  in  the  Arctic  regions,  but  I  could  give  no  suit- 
rrf  thirr  maidna  traaajjinn  fi  nai  tan  iJumHtr  t" 
the  single  wave  at  the  latitude  CO0.  It  now  appears  that  the 
inrnal  waves  are  due  to  temperature  effects  aad  eonrec- 
tts  in  the  lower  strata,  as  within  COO  aMitorn  of  the 
surface,  and  that  above  them  from  600  meters  to  3000  meters 
there  exists  a  single  temperature  wave,  located  halfway  be- 
tween them,  which  likewise  m  produced  as  the  result  of  the 
temperature  distribution  in  the  fewer  strata.  Now,  since  in 
the  temperate  zones,  the  double  temperature  wares  exist  at 
few  levels  aad  the  single  temperature  ware  at  high  Ininla,  ft 
is  quite  likely  that  this  single  wave  descends  to  the  surface  in 
the  Ttolmr  T*mn_  aad  indacea  the  single  pressure  wave  which 
ganies  it  Than,  the  single  temperature  and  pressure 
rest  on  the  surface  in  the  polar  zones,  but  pass  orer- 
s  an  arch  in  the  temperate  aad  the  tropical  zones, 
higher  in  the  Tropics  than  in  the  middle  latitudes.  This  is 
quite  similar  to  the  distribution  of  the  aqueous  vapor  con- 
tents ia  an  arch,  and  it  is  probable  that  the  positire  (+)  ions 
travel  along  this  high  HIIIBBBIU  arch  through  the  earth's  at- 
mosphere rather  than  by  any  other  route  The  rectors  of 
figs.  59,  CO  show  fla*  long  rectors  occur  in  the  Polar  Zone, 
and  in  the  latitudes  between  the  eastward  drift  of  the  tem- 
aad  the  aeatmard  drift  of  the  Tropics,  that  is  to 
say,  in  the  belts  of  the  earth  where  the  high  pressure  distri- " 
Imiiiaal  come  to  the  surface.  The  cloud  belts  of  the  Temper- 
ate Zone,  latitudes  40°  to  50°,  and  near  the  equator,  +10°  to 
— 10°,  apparently  iaiamli  the  circulation  of  the  streams  of 
ions  and  so  produce  short  disturbing  rectors  in  those  belts. 


Fina 
from 
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UT,  br  comparing  the  diurnal  -wind  rectors,  as  deduced                TAZI^E 
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they  BMBjaaijeiiz*  closely  with  the   other  results  of  this 

11,  —  Vectors  cffhe  diurnal  magnetic  deflecting  force*. 

azimuth  unsle,  K.  =0*,  W.i^ne0,  fc.  =  180°,  E.  =  270. 
in  ternw   ul  D.OOOU1  C.  Or.  fc.  unit. 
vertical  angle,  positive  to  zenith. 

rsis.     I  maT  remark  in  conclusion,  that  "there  seems  to  be 
i  need  to  adopt  the  theory  of  Arrhenius,  that  the  mag- 

*-» 

IWteuary. 

Starch. 

April. 

;  disturbances  are   due  to  a  bombardment  of  the   Bolar     Hours.  - 
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V.— THE  VARIABLE  ACTION  OF  THE  SUN  AND  ITS  EFFECT  UPON  TERRESTRIAL  WEATHER  CONDITIONS. 


APPLICATIONS  TO  THE  PROBLEMS  OF   THE  WEATHEB. 

The  foregoing  correlation  of  the  connections  between  the 
phenomena  of  temperature,  pressure,  vapor  tension,  atmos- 
pheric electricity,  ionization,  and  magnetic  vectors  seems  to 
give  a  natural  unity  to  these  data  which  have  been  detached 
from  one  another  in  the  previous  scientific  researches.  The 
entire  train  of  causes  and  effects  is  arranged  by  it  in  a  satis- 
factory sequence,  so  that  we  are  for  the  first  time  in  a  position 
to  summarize  the  masses  of  evidence  lying  before  us.  It  will 
be  now  possible,  having  a  clear  working  hypothesis  before  us, 
to  indicate  the  proper  manner  of  continuing  the  investiga- 
tions with  every  prospect  of  reaching  a  successful  practical 
result.  I  propose  in  the  remaining  papers  of  this  series  to 
lay  down  a  working  program  for  American  meteorologists  to 
use,  including  in  that  term  those  astrophysicists  who  are 
interested  in  the  sources  of  our  radiant  energy,  as  well  as  the 
climatologist  and  the  forecaster  who  are  concerned  with  the 
effects  of  radiation  upon  climatic  and  weather  variations. 
The  first  paper  will  contain  a  popular  statement  of  the  general 
conditions;  the  second,  a  more  technical  account  of  the  theo- 
retical aspects  of  the  problem  of  cosmical  meteorology ;  and  the 
third,  a  description  of  the  organization  of  the  Mount  Weather 
Research  Observatory  which  is  designed  to  mediate  between 
the  theoretical  and  the  practical  sides  of  the  subject. 

THE    SUN    A   VARIABLE   STAR. 

In  order  to  bring  out  the  underlying  reason  for  believing 
that  variable  solar  action  is  responsible,  at  least  indirectly,  for 
changes  in  the  terrestrial  weather  from  year  to  year,  it  is  nec- 
essary to  show  in  what  way  the  sun  is  itself  unequal  in  its  in- 
ternal movements.  The  sun  is  an  immense  solid-liquid  mass, 
866,000  miles  in  diameter,  surrounded  by  a  gaseous  envelope  • 
which  gradually  changes  to  rarefied  matter  similar  to  that 
seen  in  vacuum  tubes.  Recent  computations  indicate  that  at 
the  center  of  the  sun  there  is  a  nucleus  which  instead  of  be- 
ing gaseous  is  nearly  as  solid  as  the  interior  of  the  earth,  with 
a  temperature  of  about  10,000°  centigrade;  the  average 
density  of  the  whole  sun  is  1.43  times  that  of  water,  and  this 
is  located  at  half  the  distance  from  the  center  to  the  surface; 
the  surface  density  is  not  far  from  0.37  that  of  water,  and  its 
temperature,  according  to  my  calculation,  ranges  between 
7000°  and  6000°  centigrade;  at  the  surface  there  is  a  sudden 
transition  from  liquids  to  gases,  which  occurs  as  an  explosion, 
caused  by  the  uprush  of  liquids  from  the  interior.  The  solar 
mass  in  such  a  physical  state  while  rotating  on  its  axis  sets  up 
a  peculiar  circulation,  in  consequence  of  which  at  the  surface 
a  huge  wave  is  formed  like  a  tide  that  advances  most  rapidly 
in  the  equatorial  belt 

The  body  of  the  sun  is  divided  up  into  layers  of  different 
temperatures,  like  a  set  of  dice  boxes  inside  one  another,  the 
longest  axis  extends  through  the  sun  from  pole  to  pole,  and 
these  slide  by  one  another  at  different  velocities.  This  pro- 
duces a  stronger  discharge  of  warm  material  in  the  polar  re- 
gions than  near  the  equator,  so  that  on  the  sun  the  heat  is 
greatest  at  the  poles,  reversing  the  conditions  with  which  we 
are  familiar  in  the  earth's  atmosphere. 

The  evidence  for  these  facts  is  found  in  a  study  of  the  ( 1 ) 
sun  spots,  which  occur  in  belts  within  35°  of  the  equator;  (2) 
the  faculse  or  fleecy  cloud-like  forms  found  on  all  parts  of 
the  sun's  surface,  but  most  abundantly  around  the  spots;  (3) 
the  prominences  or  gaseous  flames  projected  in  all  latitudes 
above  the  disk;  and  (4)  the  coronas,  which  extend  to  great 


distances  from  the  surface  and  somewhat  resemble  auroras 
in  their  nature. 


FIG.  64. — Retardation  of  rotation  in  different  zones  of  the  sun. 

The  visible  surface  is  divided  for  convenience  into  succes- 
sive zones  beginning  at  the  equator  as  shown  on  fig.  64,  where 
the  advancing  equatorial  wave  is  indicated,  the  time  of  rota- 
tion being  marked  in  different  latitudes  with  26.68  days  at 
the  equator,  increasing  to  29.50  days  at  the  poles.  The  time 
of  the  rotation  of  the  internal  solid  nucleus  is  not  known. 
There  are  some  arguments  for  supposing  it  to  be  26.00  days, 
and  others  for  making  it  26.68  days,  but  the  subject  has  not 
yet  yielded  to  study.  The  above  periods  of  rotation  are  those 
seen  from  the  earth  as  it  passes  around  the  sun  in  its  orbit  of 
365  days. 

Fig.  65  gives  an  excellent  idea  of  the  visible  surface.  This 
is  mottled  with  cloud-like  forms  resembling  the  heads  of 
cumulus  clouds,  and  probably  they  represent  the  tops  of 
columns  of  liquid  or  gaseous  matter  rising  from  the  interior; 
there  are  three  minute  sun  spots  to  be  seen  on  it,  and  exten- 
sive regions  of  white  calcium  flocculi  in  the  sun-spot  belts. 
The  spectroheliograph  has  developed  the  power  to  make 
pictures  like  this  at  different  levels  in  the  sun's  atmosphere, 
representing  sections  through  it,  so  that  the  action  of  the 
vapors  and  gases  surrounding  a  spot  can  be  studied  at  several 
elevations,  just  as  we  make  out  the  cloud  forms  at  different 
levels  in  the  earth's  atmosphere  by  their  types.  In  this 
picture  the  details  are  quite  perfectly  brought  out. 

Fig.  66  is  an  illustration  of  a  great  sun  spot  and  the  clouds 
or  the  flocculi  in  its  neighborhood.  Three  or  four  such  sec- 
tion pictures  are  made  one  over  the  other,  wherein  the  forms 
change  gradually  from  the  lowest  level  to  the  highest.  It  is 
very  probable  that  the  true  circulation  in  the  region  of  the 
spots  can  be  determined  by  examining  the  details  of  such 
pictures.  The  sun  spots  of  the  winter  1904-5  closely  resemble 
the  one  in  this  illustration  in  size  and  appearance. 

Fig.  67  gives  some  examples  of  quiescent  and  eruptive  promi- 
nences or  hydrogen  flames,  as  observed  at  Kalocsa  Observa- 
tory. The  forms  resemble  flash  illuminations  in  clouds  dur- 

39 


40 


ing  storms  where  no  lightning  discharge  occurs,  and  are 
probably  due  to  the  light  from  the  photosphere  passing 
through  rarefied  layers  of  gas,  in  about  the  same  way  that  the 
aurora  illumination  is  formed.  Electrical  glow  discharges  and 
magnetic  forces  are  probably  in  operation  at  the  same  time. 
The  eruptive  prominences  are  due  to  uprushes  of  gas  explod- 
ing from  the  surface.  The  liquids  in  the  interior  are  at  very 
great  pressure  and  temperature,  but  on  reaching  the  surface 
this  pressure  diminishes  suddenly  and  the  liquid  explodes 
into  gaseous  formations  such  as  are  shown.  Enormous  ve- 
locities up  to  1000  miles  per  hour  are  indicated,  and  great  al- 
titudes up  to  300,000  miles  above  the  surface  have  been  noted. 

Beyond  the  limits  of  the  gaseous  constituents  of  the  sun 
extends  the  corona  which  reaches  altitudes  of  from  1,000,000 
to  5,000,000  miles  above  the  sun's  surface.  The  lower  section  of 
fig.  68  gives  four  typical  shapes,  one  at  the  minimum  of  solar 
activity,  one  at  the  maximum,  one  at  the  rising,  and  one  at 
the  falling  phase.  At  the  minimum  the  polar  region  is  capped 
with  a  ray-like  structure  in  which  the  streamers  bend  away  to 
either  side,  as  if  they  were  the  lines  of  force  in  a  magnetic  field 
surrounding  a  spheroidal  magnet.  At  the  maximum  of  the 
period  the  coronal  forms  are  confused  and  no  definite  structure 
is  preserved,  indicating  that  some  cause  is  operating  to  obscure 
the  beautiful  magnetic  structure  seen  at  the  minimum  when 
the  sun  is  not  very  active.  The  corona  of  the  sun  can  not 
be  observed  except  during  total  eclipses,  but  it  is  found  by 
comparing  the  forms  secured  during  the  past  40  years  that 
it  passes  through  a  well  defined  cycle,  repeated  in  about  11 
years,  as  is  indicated  in  the  diagram.  The  next  total  eclipse 
will  occur  on  August  29-30,  1905,  and  will  be  visible  in  Spain 
and  northern  Africa.  Parties  are  already  being  formed  in  the 
United  States  to  make  observations  on  that  occasion. 

The  passage  from  a  quiet  to  a  strongly  agitated  condition 
•of  the  sun  is  marked  also  by  other  remarkable  variations  in 
phenomena  which  are  visible  from  the  earth.  The  upper 
section  of  fig.  68  gives  the  relative  frequency  of  the  sun-spot 
area  as  computed  at  the  Greenwich  Observatory.  A  minimum 
occurred  in  1889,  a  maximum  in  1894,  and  a  second  minimum 
in  1900,  about  11  years  later.  The  height  of  the  shaded  area 
is  proportional  to  the  number  of  sun  spots  seen  on  the  sun, 
and  it  indicates  that  the  rate  of  increase  following  the  mini- 
mum is  more  rapid  than  the  rate  of  decrease  following  the 
maximum.  Similar  curves  of  sun-spot  frequency  have  been 
constructed  for  the  last  century,  and  in  them  it  is  found  that 


there  is  considerable  irregularity  in  the  curve  from  one  period 
to  another,  so  that  the  11-year  period  is  merely  an  average  of 
the  range  between  8  years  and  14  years.  On  comparing  the 
sun-spot  curve  with  the  changes  in  the  magnetic  and  electric 
fields  as  observed  on  the  earth,  that  is  to  say  with  the  posi- 
tions assumed  by  the  magnetic  needle  and  with  the  auroral 
displays  in  the  polar  regions,  it  is  shown  that  these  three 
systems  are  in  very  close  accordance,  and  it  is  conceded  that 
some  relation  of  cause  and  effect  prevails.  The  inference 
that  the  difference  in  the  number  of  spots  is  the  cause  of  the 
corresponding  change  in  the  earth's  electricity  or  magnetism 
is  not  sustained  by  more  minute  examination  of  the  details, 
except  in  a  general  way.  The  better  theory  is  that  the  inter- 
nal solar  action  produces  all  of  these  phenomena  simultane- 
ously, as  the  effects  of  an  underlying  cause  which  is  not  yet 
fully  understood. 

We  can,  perhaps,  convey  some  idea  of  the  present  state  of 
the  investigation  in  the  following  way.  The  difficulty  of  the 
research  has  been  due  to  the  fact  that  the  sun  spots  are  only 
a  sluggish  register  of  the  true  solar  action  which  causes  the 
variable  weather  conditions,  and  it  has  been  a  great  task  to 
discover  a  better  pulse.  In  1894  the  author  published  some 
results  of  a  study  of  the  meteorological  conditions  in  the 
United  States  for  the  interval  1878-1893,  in  which  it  was 
found  that  the  barometric  pressure  and  the  temperature  vary 
slightly,  not  only  in  an  11-year  period,  but,  also,  in  a  3-year 
period  which  is  more  clearly  defined.  In  the  same  work  it 
appeared  that  the  average  position  of  the  storm  tracks  in  the 
United  States  sways  up  and  down  in  latitude,  and  also  that 
the  speed  with  which  the  storms  drift  eastward  varies  in  the 
same  short  period.  The  annual  magnetic  field  gives  both 
periods  in  combination,  the  3-year  period  superposed  upon 
the  11-year  period,  thus  making  the  inference  probable  that 
both  periods  in  the  meteorological  and  magnetic  elements 
depend  upon  solar  operations.  Unfortunately  the  sun  spots 
show  us  the  11-year  period  strongly  and  the  3-year  period 
very  feebly.  This  point  has  recently  been  cleared  up  by  a 
study  of  the  solar  prominences,  which  have  been  continuously 
observed  by  the  Italian  spectroscopists  since  1871. 

Fig.  69  shows  that  great  variations  occur  in  the  number  of  the 
prominences  and  the  faculse,  the  former  being  represented  by 
the  red  marks  on  the  diagram,  and  the  latter  by  the  blue 
marks.  In  the  year  of  minimum  activity,  1889,  both  promi- 
nences and  faculffi  are  very  few  in  number,  but  in  the  year  of 


FIG.  68. — The  upper  section  shows  the  variation  in  the  relative  number  of  sun  spots  in  a  11-year  period  and  the  lower  section  shows  the  corre- 
sponding changes  in  the  form  of  the  solar  corona  in  passing  from  minimum  to  maximum  and  back  to  minimum. 


41 


maximum  activity,  1894,  they  are  very  abundant  in  the  central 
zones,  the  prominences  extending  into  the  higher  latitudes. 


Northern  Hem  isphere . 


FIG.  70. — Relative  frequency  of  the  occurrence  of  hydrogen  flames  as 
seen  on  the  edge  of  the  Northern  Hemisphere  of  the  sun  in  a  spectro- 
scope: the  distribution  on  the  Southern  Hemisphere  is  similar  to  that 
shown  on  the  northern. 

These  eruptions  on  the  surface  of  the  sun  move  up  and  down 
the  solar  disk  by  a  law  of  their  own,  and  this  must  depend 
upon  the  internal  energy  of  the  sun,  which,  like  a  variable 
star,  is  passing  through  a  series  of  periodic  convulsions  in  its 
process  of  evolution.  Lockyer,  in  1902,  published  the  result 
of  his  discussion  of  the  prominences,  as  they  occur  in  each  10- 
degree  zone  between  the  two  poles  of  the  sun.  Thus,  it  is 
seen  by  fig.  70,  for  the  Northern  Hemisphere,  how  different 
the  distribution  of  the  prominences  is  in  latitude.  In  the  equa- 
torial regions,1  where  the  spots  prevail,  the  11-year  period  is 
very  pronounced,  though  there  are  signs  of  the  3-year  period 
in  connection  with  it.  On  the  other  hand,  in  the  higher  lati- 
tudes,1 the  11-year  period  diminishes  in  importance  and  the 
3-year  period  supersedes  it. 

THE  SYNCHRONOUS  METEOROLOGICAL  CONDITIONS  ON  THE  EARTH. 

Now,  it  happens  that  the  frequency  variation  of  the  solar 
prominences  in  the  higher  latitudes  gives  the  key  that  was 

1  Zones,  (+  10°  0°),  (+  20°  +  10°).  (+  30°  +  20°). 
1  Zones,  (+  40°  +  30°),  (+  50°  +  40°),  (+  60°  +  50"). 


wanted  to  enable  us  to  study  the  meteorological  conditions  in 
the  earth's  atmosphere  with  some  prospect  of  success.  This 
variation  shows  that  the  meteorological  pulse  is  registered 
most  favorably  not  in  the  sun-spot  belts,  but  in  the  zones  of 
the  sun  corresponding  with  the  temperate  zones  of  the  earth, 
from  latitude  30°  to  60°.  In  the  polar  zones  in  certain  years 
the  prominence  frequency  is  very  well  marked,  and  these  years 
correspond  with  the  years  of  special  activity  in  the  earth's 
electric  and  magnetic  fields. 


FIG.  71. — Comparison  of  the  annual  changes  of  the  prominences  on  the 
sun  and  the  temperatures  and  pressures  on  the  earth  during  the  years 
1872-1900.  ' 

In  order  to  extend  the  comparison  of  the  solar-terrestrial 
conditions  further,  I  computed  the  annual  mean  pressure  and 
annual  mean  temperature  for  the  series  of  years,  1872-1900, 
over  many  portions  of  the  earth,  comprising  records  for  several 
hundred  stations.  They  were  grouped  together  by  countries 
and  a  few  of  the  curves  are  brought  together  in  fig.  71.  In 
the  upper  section  of  this  figure  the  prominence  frequency  on 
the  sun  is  averaged  for  all  zones,  and  the  resulting  curve  con- 
tains a  3-year  period  superposed  upon  the  11-year  period.  The 
middle  section,  marked  "temperatures,"  contains  temperature 
curves  from  the  tropical  and  temperate  zones,  and  it  is  easily 
seen,  by  comparing  the  crests  with  the  solar  curve  at  the  top, 
that  in  spite  of  some  irregularities  there  is  a  tendency  to  form 
the  same  number  of  crests  and  to  make  them  fall  on  the  same 
years  as  the  crests  in  the  prominences.  The  third  section, 
marked  "pressures,  "gives  a  few  curves  of  the  variations  in  the 
annual  pressures  and  these  conform  quite  closely  to  the  same 
system.  Each  curve  ought  to  be  compared  with  the  solar  curve 
by  itself,  to  judge  of  the  general  fact  of  agreement.  It  should, 
however,  be  observed  that  this  agreement  is  not  everywhere 
direct,  but  that  in  certain  regions  an  inversion  takes  place. 
Thus,  the  pressures  do  not  increase  simultaneously  all  over  the 
earth  in  one  year  and  decrease  in  another  year,  rather  there 
is  a  general  surging  by  which  the  atmosphere  is  piled  up  in 
one  region  and  lowered  in  another  during  the  same  year.  This 
is  necessary  in  order  to  avoid  the  difficulty  of  making  the 
total  weight  of  the  earth's  atmosphere  vary  from  year  to  year. 
When  the  pressure  is  generally  high  in  North  or  South  Amer- 
ica, it  is  low  in  Asia,  the  Indian  Ocean,  and  Australia.  This 


42 


condition  is  brought  about  by  some  profound  modification  in 
the  circulation  of  the  earth's  atmosphere,  by  which  high  areas 
tend  to  form  in  one  hemisphere  at  the  same  time  that  low  areas 
prevail  in  the  opposite  hemisphere.  In  a  similar  way  the 
changes  of  temperature  from  year  to  year  are  such  that  in  the 
tropical  zones,  where  the  sun  shines  fully  on  the  earth's  sur- 
face, temperatures  rise  and  fall  directly  with  the  solar  promi- 
nence frequency;  but  in  the  middle  latitudes  of  the  earth  the 
opposite  or  reverse  conditions  of  temperature  prevail.  Hence, 
when  solar  activity  increases  and  more  spots  or  prominences 
can  be  seen,  there  is  an  increase  of  heat  in  the  earth's  Tropics, 
and  this  produces  an  increase  in  the  circulation  of  the  entire 
atmosphere.  The  warm  air  of  the  Tropics  rises  more  rapidly 
than  usual,  the  cold  air  of  the  upper  strata  over  the  temperate 
zones  pours  down  vigorously  upon  the  United  States,  Europe, 
and  Asia,  and  these  countries  are  covered  with  a  rapid  succes- 
sion of  pronounced  cold  waves,  such  as  have  marked  the  years 
1904  and  1905. 

The  increase  in  solar  activity  shows  itself  in  yet  another  way. 
By  putting  together  the  tables  of  prominences  so  as  to  study 
their  behavior  in  longitude,  that  is  around  the  sun  in  the 


same  zones,  it  has  been  found  that  the  retardation  of  the  solar 
rotation  in  the  higher  latitudes  relative  to  the  primary  equa- 
torial period  of  26.68  days,  sways  backward  and  forward  in 
harmony  with  the  same  prominence  frequency  curve.  This- 
indicates  that  the  internal  solar  energy,  in  trying  to  free 
itself  after  accumulation  and  congestion,  sends  forth  great 
waves,  which  rotate  the  circulation  in  the  polar  zones  farther 
backward.  The  visible  symptoms  of  this  operation  at  the 
surface  are  changes  in  the  number  and  location  of  the  promi- 
nences, the  faculffi,  the  sun  spots,  the  granulation  of  the 
photosphere,  and  in  the  form  and  extent  of  the  great  coronal 
streamers.  Besides  this  visible  effect  of  the  internal  action, 
there  is  the  more  important  and  invisible  radiation  which 
streams  from  the  sun  and  falls  upon  the  earth. 

Besides  the  general  synchronism  in  the  solar  action  just 
outlined,  we  have  a  corresponding  movement  in  the  earth's 
atmosphere  embracing  the  magnetic  and  electrical  forces,  the 
pressure,  temperature,  vapor  tension,  and  precipitation.  Con- 
flicting evidence  will  no  doubt  be  reconciled  by  a  more 
thorough  study  of  the  underlying  facts  of  inversion,  and  gen- 
erally the  entire  subject  needs  most  careful  investigation. 


43 


N 


s 

FIG.  65.— Spoetroheliograph  of  the  sun,  August  12,  1903,  taken  at  the  Yerkes  Observatory,  showing  the  spots,  flocculi,  and  general  appearance  of 

the  bright  surface  of  the  photosphere. 


44 


FIG.  66. — Spectroheliograph  of  the  sun  spot  of  October,  1903,  showing  the  calcium  flocculi  surrounding  it. 


Fio.  6". — Typical  forms  of  the  solar  prominences  or  red  hydrogen  flames. 


45 


60 


50 


40 


30 


20 


10 


—  10 


—20 


—80 


-40 


-50 


-60 


3 


V; 


Prominences  and  'Faculae  inl88dtheyearofmiriiznt£m  activity: 


Pi~oznirte2zce&  arzd  '  JFacul<zeinl894  tkejrearof 


activity: 


FIG.  69. — The  frequency  and  size  of  the  faculte  and  the  prominences  change  from  year  to  year,  as  shown  by  examples 
from  the  minimum  in  1889  and  the  maximum  in  1894.     Faculae  in  blue.     Prominences  in  red. 


VI.— GENERAL  REVIEW  OF  THE  STATUS  OF  COSMICAL  METEOROLOGY. 


COSMICAL   METEOROLOGY. 

A  great  advance  is  taking  place  in  the  science  of  meteor- 
ology, and  this  has  been  brought  about  during  the  past  fifteen 
years.  It  has  been  due  to  two  causes,  the  growth  of  modern 
physics,  and  the  extension  of  observations  into  the  strata  of 
atmosphere  high  above  the  ground.  The  new  theories  of  the 
constitution  of  matter,  in  which  the  emphasis  is  laid  upon  the 
electrical  nature  of  the  ultimate  units  of  which  atoms  and 
molecules  are  constructed,  and  the  transmission  of  energy  in 
ether  waves  across  great  distances,  have  disposed  the  scientific 
world  to  examine  old  conclusions  from  a  very  different  point 
of  view. 

(1)  In  1890  the  high  temperature  of  the  sun  seemed  to  justify 
its  exclusion  from  the  class  of  magnetized  spheres,  and  thus 
to  separate  it  from  the  group  containing  the  earth.     Now, 
however,  there  are  numerous  arguments  which  make  it  neces- 
sary to  reconsider  that  view,  and  to  admit   that  the  sun  is 
probably  a  highly  magnetized  sphere  which  sustains  a  mag- 
netic field  embracing  the  earth  in  its  action. 

(2)  Then  the  radiation  from  the  sun  was  considered  a  con- 
stant quantity,  but  now,  there  are  so  many  lines  of  converg- 
ing evidence  to  show  this  may  not  be  true,  that  the  subject 
has  become  one   of  serious  investigation,  and  the  belief  is 
widespread  that  the  sun  is  a  variable_  star  transmitting  its 
energy  to  the  earth  in  such  ways  as  to  produce  synchronous 
changes  in  its  meteorological  and  climatic  conditions. 

(3)  In   those  days  the  theories  of  the  general  circulation 
of  the  atmosphere,  as  formulated   by  Ferrel,  were  generally 
considered  to  be  correct,  but  the  explorations  of  the  atmos- 
phere, by  means  of  theodolites,  nephoscopes,  kites,  and  bal- 
loons have  seriously  discredited  all  except  the  central  idea. 

(4)  In   the  same   way,   the  Ferrel  theory  as  well  as   the 
Oberbeck  theory  of  the  circulation  of  the  air  in  local  cyclones 
and  anticyclones,  have  both  become  obsolete  and  a  new  type 
of  vortex  is  being  considered  as  applicable  to  them. 

It  is  evident  that  a  reconstruction  of  ideas  is  in  order  all 
along  the  line,  and  that  meteorology  is  passing  through  a 
transition  period  in  its  development.  The  general  outcome  is 
to  raise  meteorology  from  a  subject  which  was  the  peculiar 
property  of  the  climatologist  and  the  forecaster  into  one  of 
vital  interest  in  cosmical  science,  and,  indeed,  one  which  is 
essential  to  the  progress  of  astrophysical  astronomy.  This 
change  from  an  empirical  and  statistical  basis,  re  quiring  merely 
clerical  functions  in  those  practising  the  art,  to  a  plan  of  opera- 
tions involving  the  highest  ranges  of  astronomy,  mathematics, 
and  physics  in  its  students,  is  one  of  the  most  hopeful  signs  of 
the  times.  Meteorology  has  really  languished  for  the  lack  of 
a  demand  for  high  grade  scholarship,  but  the  knowledge  that 
the  observations  of  pressure,  temperature,  vapor  tension,  and 
vectors  of  motion  in  the  earth's  atmosphere  have  an  astro- 
nomical value,  will,  of  course,  facilitate  the  introduction  of 
methods  of  precision  in  the  observations  and  in  the  computa- 
tions leading  to  a  discussion  of  the  results. 

The  research  that  is  bringing  about  this  change  in  meteor- 
ology has  been  one  of  extraordinary  difficulty  for  two  or  three 
reasons.  In  the  first  place,  by  the  very  nature  of  the  case, 
meteorology  must  depend  largely  upon  handling  great  masses 


of  data,  at  least  till  a  higher  stage  of  classification  and  unifi- 
cation of  the  laws  has  been  attained,  because  the  action  of  the 
several  elements  differs  greatly  from  one  station  to  another 
over  the  earth,  and  each  station  must  be  considered  on  its  own 
merits.  In  astronomy,  on  the  other  hand,  a  ready  concentra- 
tion of  observations,  made  in  various  places  upon  the  same 
celestial  object,  is  practicable,  and  this  coordination  leads  more 
rapidly  to  a  final  set  of  constants  and  formulae.  The  astro- 
nomical ephemeris,  embracing  the  positions  of  the  sun,  moon, 
planets,  and  stars,  with  their  characteristic  phenomena,  are, 
thus,  readily  made  up,  and  by  successive  comparisons  between 
predicted  and  observed  places  a  progressive  accuracy  has  been 
developed.  Meteorology  has  not  yet  attained  the  dignity  of 
the  most  elementary  kind  of  ephemeris,  but  has  been  content 
with  striking  a  rough  mean  or  normal  from  a  large  mass  of 
crude  observations.  This  method  has  no  doubt  been  sufficient 
for  climatological  statistics,  and  for  such  forecasts  as  have 
been  attempted  during  the  past,  but  with  the  entrance  of  cos- 
mical problems  into  the  field  of  work  that  sort  of  procedure 
is  entirely  inadequate. 

A   METEOROLOGICAL    EPHEMEBIS. 

As  already  mentioned,  the  first  line  of  improvement,  hav- 
ing in  view  the  ultimate  construction  of  a  true  meteoro- 
logical ephemeris,  is  a  careful  discussion  of  the  existing 
data.  An  examination  of  the  available  observations  in  the 
various  portions  of  the  earth,  convinced  me  several  years 
ago  that  for  cosmical  meteorology  they  are  well  nigh  value- 
less in  their  present  state.  There  has  been  an  incessant 
change  in  the  conditions  under  which  the  observations  were 
made,  following  the  exigencies  of  administration,  or  in  conse- 
quence of  the  lack  of  scientific  purpose  and  method  in  con- 
ducting the  reductions.  Thus,  the  hours  of  observation  have 
been  changed,  and  this  has  broken  up  the  homogeneity  of  the 
series;  the  elevation  of  the  station  has  been  frequently  altered; 
the  exposure  of  the  instruments  to  the  weather  has  been  modi- 
fied, often  radically,  by  the  growth  of  our  large  cities;  hence 
it  is  that  a  pure  series  of  data  extending  over  several  years  is 
not  a  common  feature  of  any  meteorological  service.  The 
ephemeris  of  this  science  must  take  account  of  a  list  of  natural 
phenomena  different  from  that  found  in  the  astronomical 
almanacs,  namely,  the  pressure,  the  temperature,  the  vapor 
tension,  and  the  wind  vectors  in  the  atmosphere  of  the  earth, 
at  the  least;  the  frequency  of  the  spots,  the  faculae,  the 
prominences  on  the  sun;  the  intensity  of  the  lines  in  the 
spectrum,  distinguishing  those  of  solar  from  those  of  terrestrial 
origin;  the  relative  absorption  of  the  radiation  in  the  solar 
and  the  terrestrial  envelopes,  respectively;  the  strength  of 
the  electric  and  the  magnetic  fields  in  the  earth's  atmosphere, 
including  the  auroras,  the  ionization,  the  electric  potential, 
and  the  coefficient  of  dissipation.  In  all  these  cases,  for  the 
construction  of  an  ephemeris,  it  is  not  sufficient  to  strike  a 
mean  value  from  a  series  of  observations  extending  over  a 
number  of  years,  where  the  individual  years  are  not  homoge- 
neous one  with  the  others.  "What  we  want  is  a  series  of 
correct  yearly  and  monthly  residuals  relative  to  a  central 
normal  or  mean  value,  wherein  it  is  certain  that  the  apparent 

47 


48 


variations  from  year  to  year  are  not  due  to  faulty  instruments 
and  inadequate  modes  of  observing,  nor  to  incorrect  and  in- 
sufficient methods  of  computing.  There  is  an  immense  mass 
of  meteorological  data  which  in  its  present  state  has  no  value 
for  a  cosmical  science,  because  the  accidental  errors,  that  is 
those  which  can  be  controlled  and  ought  to  be  eliminated  in 
forming  a  truly  homogeneous  series,  are  larger  than  the  re- 
siduals which  can  correctly  be  attributed  to  the  variable  solar 
action.  The  margin  of  variability  induced  at  the  earth  by  the  un- 
steady energy  of  the  sun  is  quite  narrow,  and  there  is  nothing  to  be 
squandered  by  poor  workmanship  if  any  useful  results  are  to  be  ac- 
complished in  practical  meteorology.  There  is  nothing  scientific 
in  attributing  to  the  sun's  action  those  changes  which  pertain 
to  the  inaccurate  observer  or  to  bad  methods  of  working 
the  instruments,  nor  is  there  any  justification  for  comparing 
good  solar  observations  with  bad  meteorological  observations. 
If  cosmical  meteorology  is  to  be  established  then  all  rough 
and  ready  methods  must  be  abandoned,  and  the  work  of  com- 
puting and  discussing  the  data  must  be  placed  in  the  hands 
of  physicists  and  astrophysicists  who  possess  scientific  instincts 
and  training.  It  is  only  by  acquiring  long  series  of  accurate 
residuals  in  all  the  elements  enumerated  above,  that  is  to  say 
exact  values  for  each  month  and  year  at  the  selected  standard 
stations,  that  a  suitable  ephemeris  can  be  constructed.  Upon 
the  successful  accomplishment  of  this  purpose  depends  the 
establishment  of  cosmical  meteorology  and  the  detection  of 
the  laws  controlling  the  many  interrelated  forces  which  culmi- 
nate in  weather  and  climatic  conditions.  I  maintain  that  the 
seasonal  and  yearly  changes  in  climate,  which  each  country 
experiences,  depend  upon  the  variable  output  of  the  solar 
energy,  as  recorded  in  the  circulation  of  the  sun's  atmosphere 
and  in  our  own  atmosphere,  and  the  sequence  of  these  varia- 
tions is  a  proper  subject  for  scientific  examination.  This  work 
in  one  sense  is  common  to  the  entire  earth,  and  yet  each 
country  has  its  own  climatic  effect  to  be  accounted  for  in  the 
general  integration.  No  country  can  transfer  its  task  to  an- 
other, and  each  has  enough  to  do  to  take  care  of  its  own  obser- 
vations. To  some  extent  international  cooperation  is  desire- 
able  and  practicable,  but  on  the  whole  each  climatic  region 
must  work  out  the  problem  for  itself.  There  is  a  common 
solar-terrestrial  circulation  which  flows  throughout  the  en- 
tire cosmical  system,  yet  each  country  has  a  pulse  of  its 
own,  and  this  must  be  discovered  and  analyzed  before  there 
can  be  any  expectation  of  establishing  an  efficient  seasonal 
meteorology. 


PRESENT    STATUS    OF    THE    REDUCTIONS. 

My  own  work  has  for  many  years  been  concerned  in  re- 
ducing the  crude  meteorological  data  for  the  sun,  the  earth 
generally,  and  especially  for  the  United  States,  into  standard 
conditions,  from  which  the  first  approximately  correct  re- 
siduals may  be  attained.  The  task  has  been  far  beyond 
my  power,  with  the  resources  at  command,  and  the  work 
is  not  yet  finished.  Thus,  (1)  from  1878  to  1893  the  mag- 
netic vectors  have  been  properly  computed,  but  they  had 
to  be  extended  by  graphic  methods  back  to  1841  and  for- 
ward to  1903  in  order  to  get  even  a  glance  at  the  fun- 
damental law.  (2)  The  diurnal  magnetic  vectors  were 
worked  out  for  30  stations  and  they  are  in  good  order. 
Neither  of  these  works  have  been  published.  (3)  The  pres- 
sures for  the  United  States,  1873  to  the  present  time,  have  been 
thoroughly  recomputed  and  they  are  in  a  satisfactory  state. 
(4)  The  temperatures  are  in  process  of  reconstruction,  but  the 
task  is  much  more  difficult  than  in  the  case  of  the  pressures 
and  the  work  is  not  finished.  (  5  )  The  reductions  of  the  vapor 
tensions  are  being  carried  along  with  that  of  the  temperatures, 
and  they  are  only  partly  completed.  There  have  never  been 
any  vapor  tension  normals  available  in  the  United  States. 


(6)  All  the  data  of  atmospheric  electricity  are  in  a  chaotic 
state  and  need  complete  revision.  (7)  The  ephemeris  of  rela- 
tive sun-spot  numbers  is  in  good  condition  in  consequence  of 
the  work  of  Wolfer.  (8)  The  prominences  and  faculse  have 
been  thoroughly  discussed  by  me,  but  the  results  have  not  been 
published.  (9)  In  the  variation  of  the  spectrum  lines,  and 
in  the  variability  of  the  solar  radiation  as  disclosed  by  the 
actinometer  and  bolometer,  it  has  only  quite  recently  been 
recognized  that  there  is  a  real  problem  to  be  worked  out,  and 
we  have  as  yet  no  true  series  of  observations  to  classify. 

It  is  evident  from  this  statement  that  for  the  United  States, 
where  this  plan  of  reducing  the  observations  has  been  system- 
atically in  operation  for  several  years,  there  remains  much 
computing  to  be  done  before  we  can  begin  to  put  our  meteor- 
ological ephemeris  together.  Until  this  is  accomplished  there 
can  be  no  attempt  to  take  up  the  problem  of  seasonal  fore- 
casting, and  the  quicker  this  work  is  finished  the  better  for 
science  in  all  its  astrophysical  branches.  For  it  is  quite 
probable,  judging  from  the  exposition  contained  in  the  pre- 
ceding papers  of  this  series,  that  there  exists  a  beautiful  yet 
sensitive  network  of  forces  reaching  from  the  sun  to  the  sur- 
face of  the  earth,  by  which  we  can  learn  to  read  the  signs  of 
the  climate,  and  we  may  hope  to  be  able  to  learn  to  forecast 
it  somewhat  in  advance  by  a  natural  system  of  extrapolation. 
In  the  midst  of  this  concatenation  of  forces  the  terrestrial 
magnetic  field  stands  out  as  the  best  unifier  or  integrator.  It 
is  the  most  sensitive  and  delicate  pulse  which  we  possess, 
having  one  throb  in  the  solar  mass,  and  the  other  in  its 
synchronism  with  the  earth's  meteorological  elements.  We 
shall,  then,  in  our  further  discussions,  use  this  magnetic  sys- 
tem as  the  proper  one  about  which  to  group  all  the  other 
elements  which  are  correlated  in  this  great  solar-terrestrial 
complex. 

THE    SUN    AS    A    MAGNETIZED    SPHERE. 

The  radical  change,  gradually  brought  about  by  numerous 
physical  researches  in  our  ideas  regarding  the  ultimate 
constitution  of  matter,  by  which  we  conceive  of  atoms  as 
composed  of  dynamic  structures  of  balanced  rapidly  ro- 
tating electric  charges,  has,  also,  materially  modified  the 
attitude  of  mind  in  which  we  approach  the  problem  of  the 
magnetization  of  large  rotating  heavenly  bodies.  When  the 
atoms  were  regarded  as  hard,  highly  elastic,  nonelectrical, 
and  nonmagnetic  spheres  moving  by  the  laws  of  kinetic 
energy  in  straight  paths,  except  for  the  effect  of  collisions,  it 
was  of  course  difficult  to  prove  that  the  sun  could  be  magnetic 
of  itself  at  the  high  prevailing  temperature.  But  if  the  inte- 
grated forces  are  to  be  derived  from  electric  charges  in  very 
rapid  motion,  and  this  seems  to  be  the  case,  then  magnetic 
fields  are  essential  to  the  existence  of  every  kind  of  matter 
whether  in  large  or  in  small  masses.  Under  ordinary  condi- 
tions the  primitive  motions  of  the  ionic  charges  are  highly 
disorganized,  since  the  motions  are  in  every  conceivable  plane, 
and  the  molar  or  large  masses  do  not  show  any  outside  field 
of  force.  It  is,  however,  only  necessary  to  organize  these 
ionic  motions  relative  to  one  plane,  that  is,  to  polarize  their 
orbits,  in  order  to  produce  a  common  magnetization  within 
the  mass  and  magnetic  field  outside  this  body.  When  a  steel 
magnet  is  subjected  to  heat  the  field  is  destroyed,  simply 
because  the  minor  magnets,  as  of  the  atoms  and  molecules 
temporarily  oriented  to  one  axis,  have  been  made  disordered 
by  the  higher  class  of  collisions  which  has  been  induced  by 
the  increase  of  the  temperature.  This  experiment,  however, 
by  no  means  exhausts  the  natural  conditions  of  the  problem. 
In  a  rotating  body  like  the  sun  the  angular  velocity  induces  a 
deflecting  force  at  right-angles  to  the  momentary  motion,  of 
every  particle,  I  =  u>  q  cos  0,  depending  on  the  angular  velocity, 
and  polar  distance  velocity  in  any  linear  direction.  When  q 
is  great,  and  in  the  case  of  the  negative  ions  combined  in  the 


49 


atom,  it  may  approach  the  velocity  of  light,  I  is  also  a  com- 
paratively large  force,  so  that  a  tendency  to  run  into  vortex 
motion  is  ever  in  operation.  The  entire  mass  of  the  sun,  by 
the  general  laws  of  motion,  also  is  evidently  organized  as  a 
great  vortex  about  the  axis  of  rotation,  and  these  two  impulses 
doubtless  tend  to  polarize  the  motions  of  the  individual  atomic 
ions  in  planes  perpendicular  to  this  axis,  or  to  produce  mag- 
netization nearly  parallel  to  the  axis  of  rotation.  Since  the 
movement  of  the  negative  ions  is  in  excess  of  that  of  the  posi- 
tive ions,  the  resultant  magnetic  field  will  be  due  to  this  excess 
of  the  action  of  negative  electric  charges  above  the  positive 
charges,  since  for  a  common  direction  of  gyration  the  positive 
and  negative  charges  produce  oppositely  directed  magnetic 
field.  Finally,  if  the  negative  charges,  in  the  atomic  conflict, 
tend  to  escape  from  their  electric  bonds  and  to  roam  in  disre- 
gard of  any  structure,  then  these  negative  charges  may  well 
tend  to  accumulate  as  an  electrostatic  layer  on  the  surface  of 
the  sphere.  At  least  the  negative  body-charge  may,  as  a  whole, 
be  located  farther  from  the  center  of  the  sphere  than  the  posi- 
tive body-charge,  and  this  will  produce  internal  magnetization 
and  surface  electrostatic  charge,  such  as  the  earth  possesses, 
and  such  as  we  have  evidence  to  indicate  that  the  sun  also 
possesses.  This  dynamic  view  of  mine  comes  to  the  same  result 
as  the  static  theory  explained  by  Sutherland.1  "With  this 
introduction  I  shall  merely  mention  various  results  obtained 
in  my  researches,  which  are  at  least  circumstantial  evidence 
that  the  sun  is  a  highly  organized  magnetic  body,  and  that  the 
numerous  variations  in  its  internal  action  constitute  the  causes 
for  the  observed  changes  in  the  external  magnetic  field. 

(1)  The  polar  rays  of  the  corona,  at  least  at  minimum, 
conform  to  the  normal  lines  of  magnetic  force  on  a  sphere 
seen  in  projection  and  concentrated  in  a  ruffle  at  some  dis- 
tance from  the  pole. 

(2)  The  ions  in  the  solar  atmosphere  are  luminous  along 
rays  of  magnetic  force. 

(3)  The   coronal   poles   are    located    asymmetrically   with 
respect  to  the  axis  of  rotation  and  persist  from  one  eclipse  to 
another  in  the  same  relative  positions. 

(4)  The  sun's  external  magnetic  field,  as  measured  at  the 
earth,  is  so  arranged  that  it  has  greater  intensity  in  some 
solar  longitudes  than  in  others. 

(5)  By  using  large  masses  of  observational  material,  the 
typical  curve,  attributed  to  difference  in  solar  output  in  longi- 
tude  and  depending  for   its    existence    upon    the    structure 
of  the  sun's  nucleus,  has  been  found  to  be  reproduced  approxi- 
mately, in  the  distribution  of  the  sun  spots  and  prominences 
in  longitude,  in  the  terrestrial  magnetic  elements,  the  electric 
field,  the  barometric  pressures,  the  temperatures,  and  the  local 
cyclonic  movements  in  the  United  States. 

(6)  There  is  evidence  that  the  periods  of  rotation  in  the 
higher  latitudes  of   the    sun  fluctuate  about  a  mean  value 
synchronously  with  the  external  energy  variations,  showing 
that  the  entire  external  system  is  a  direct  effect  of  the  forces 
producing  at  the  same    time  the  interior  circulation  in  the 
mass  of  the  sun. 

(7)  The  inference  is  that  the  sun's  magnetic  field  embraces 
the  earth,  and  reaches  it  in  lines  perpendicular  to  the  ecliptic, 
falling  upon  the  polar  regions  of  the  earth  along  the  planes 
of  the  magnetic  meridians. 

THE  RADIATIONS  OF  THE  SUN. 

The  electromagnetic  radiation  of  the  sun  transports  to  the 
earth  the  other  kind  of  energy  which  is  concerned  in  the  tem- 
perature excess  prevailing  in  the  Tropics  over  that  in  the 
polar  zones,  and  produces  the  observed  general  and  local 

'A  possible  cause  of  the  earth's  magnetism,  W.  Sutherland,  Terr.  Mag. 
June,  1900;  September,  1900;  December,  1904. 


cyclonic  circulations.  The  coronal  rays,  especially  in  the 
equatorial  belts  of  the  sun,  indicate  that  there  are  other 
forces  in  operation  in  the  neighborhood  of  the  photosphere 
besides  those  already  mentioned. 

(1)  The  spreading  of  the  great  streamers  away  from  the 
plane  of  the  ecliptic  suggest  an  electrostatic  repulsion. 

(2)  The  streams  of  ions,  under  the  action  of  the  mechanical 
pressure  of  light,  move  not  in  radial  lines,  but  in  curves  as 
determined  by  the  additional  magnetic  and  electrostatic  forces 
prevailing  in  the  surrounding  space. 

(3)  It  is  impossible  to  assert  that  enough  ions  reach  the 
upper    strata    of    the   earth's   atmosphere   to    produce    the 
observed  variations  of  the  terrestrial-magnetic  and  electric 
fields  as  registered  in  the  lower  strata,  and  it  is  not  probable 
that  this  is  the  fact. 

(4)  This  radial  radiation  of  the  photosphere  may  be  to  some 
extent  variable  in  its  output,  and  so  produce  seasonal  climatic 
temperature  and  weather  variations  synchronous  with  it,  as 
registered   in   the   pressures   and   temperatures  in  different 
regions  of  the  earth. 

(5)  The  normal  equilibrium  of  the  earth's  atmosphere  is 
probably  disturbed  frequently,  from  day  to  day  and  hour  to 
hour,  by  the  interplay  of  this  complex  system  of  correlated 
forces. 

THE  METEOROLOGICAL  EFFECTS  OF  THE  SOLAR  ENERGY. 

The  problem  of  discussing  the  effects  of  the  solar  radiation 
upon  the  magnetic  and  the  electrical  fields  of  the  earth's 
atmosphere,  and  their  relations  to  the  meteorological  ele- 
ments, has  been  greatly  simplified  by  the  results  of  the 
research  contained  in  the  first  four  papers  of  this  series.  It 
has  been  shown  that  a  different  correlation  of  the  quantities 
in  consideration  can  be  made  and  that  in  this  way  the  intrac- 
table conditions  which  have  so  long  puzzled  scientists  are 
decidedly  ameliorated. 

(1)  The  fact  that  there  is  no  one  synchronism  common  to 
the  entire    earth   between   solar   and  terrestrial  causes  and 
effects,  has  been  explained  by  showing  that  the  temperatures 
synchronize  directly  in  the  tropical  zones,  but  only  inversely 
in  the  temperate  zones,  in  consequence  of  the  inverting  effects 
of  the  general  circulation ;  and  that  while  the  pressures  in  the 
Eastern  Hemisphere  respond  directly  to  the    solar  impulse, 
they  surge  inversely  to  it  in  the  Western  Hemisphere.     Simi- 
larly, the  precipitation  and  the  local  circulation  will  have  to 
be  distributed  by  regional  conditions  in  the  final  interpretation. 
This  will  reconcile  much  data  that  are  apparently  in  conflict  as 
evidence  regarding  the  existence  of  synchronism  generally. 

(2)  The  discovery  of  ionization  in  the  gases  of  the  atmos- 
phere, generated  probably  by  the  short-wave  radiation,  and  the 
determination  of  the  several  types  of  the  temperature  waves  in 
the  lower  strata  of  the  atmosphere,  lifts  the  veil  from  the 
problems  of  the  diurnal  barometric  waves,  the  electric  poten- 
tial gradient,  and  the  rate  of  change  in  the  electric  charges. 
These  seem  to  be  direct  consequences  of  the  temperature  act- 
ing upon  the  density  of  the  air  in  the  different  strata,  and  upon 
the  locality,  whether  warm  or  cold,  sought  out  by  the  ions. 

(3)  The  cause  of  the  hourly  variation  of  the  magnetic  field 
is  plainly  shown  to  reside  in  the  movements  of  the  ions  from 
one  level  to  another.     The  cause  of   the  daily  variation  of  the 
magnetic  field  is  probably  in  large  part  due  to  the  movement 
of  the  ions  from  one  hemisphere  to  the  other,  which   at   the 
same  time  produce  the  auroral  displays  simultaneously  in  each 
hemisphere,  and  the  electric  earth  currents  as  local  effects  in 
the  several  portions  of  the  circuit.     This    change  of  view  re- 
lieves us  of  the  difficulty  of  making   the  sun  "the  source  of  all 
the  energy  displayed  in  a  large  magnetic  storm,   since   the 
initial  impulse  is  due  to  that  portion  of  the  energy  disturbing 
the  normal  terrestrial  equilibrium,  while  much  of  the  observed 
effect  is  due  to  the  motion  of  the  ions  in  a  closed  terrestrial 


50 


circuit.  It  remains  to  discover  in  what  proportion  the  energy 
should  be  distributed  among  these  three  sources,  the  polar 
magnetic  field  of  the  sun,  the  variable  radiant  energy,  and 
the  terrestrial  ionic  circuit. 

(4)  It  is  now  apparent  that  in  using,  for  the  basis  of  my 
original  research,  the  magnetic  field  of  the  earth  as  a  register 
or  solar  pulse  recorder,  I  have  been  amply  justified  in  tracing 
out  through  it  as  the  intermediary  the  synchronism  between 
the  solar  surface  variations,  shown  by  the  spots,  faculse,  and 
prominences,  and  the  temperature  and  pressure  effects  at  the 
earth,  because  it  is  in  fact  an  intermediate  effect,  and  evidently 
the  most    sensitive  one  with  which  we  have  to  deal.      The 
subtile   influences    of   the  invisible  solar    radiation  may  be 
registered  in  several  ways,  as   bolometric   spectrum  curves, 
as  actinometer  integrations,  as  visible  energy  spectra,  or  they 
may  be  recorded  as  elastic  potential  effects  and  as  magnetic 
force  vectors.     The  latter  are  the  most  persistent  in  all  kinds 
of  weather,,  and  most  available  for  continuous  observations. 
It  is  only  necessary  to  determine  what  the  connecting  func- 
tions are  in  terms  of  magnetic  force,  to  infer  from  the  magnetic 
intensity  what   are  the  temperatures  within  two  miles  of  the 
ground,  in  the  midst  of  the  cyclonic  actions,  to  estimate  the 
movement  of  the  ionic  currents,  and  to  determine  the  relative 
amount  of   the  incoming  solar  radiation,  and  thence  to  learn 
much  regarding  the  variable  nature  of  the  circulation  within 
the  rotating  mass  of  the  sun. 

(5)  It  is  now  easy  to  see  that  several  lines  of   scientific 
inquiry  as  to  the  period  of  the  solar  rotation  have  been  mis- 
directed.    The  attempt  to  associate  magnetic  storms  with  the 
solar  spots  has  failed,  because  the  effective  surface  radiation 
on  a  given  meridian  of  the  sun  may  or  may  not  be  associated 
with  a  large  spot,  which  clearly  depends  upon  the  internal 
circulation  for  its  existence.     Besides  this,  the  magnetic  storm 
is  in  part  dependent  upon  distinctly  terrestrial  conditions. 
The  application  of   Schuster's  periodogram  to  the  magnetic 
declination,  in  order  to  determine  the  periodicity  of  the  solar 
residuals,  was  incorrect  for  this  reason.     While  the  magnetic 
declination  varies  with  the  season  of  the  year,  and  from  one 
year  to  another,  as  a  consequence  of  the  solar  radiation,  this 
component  is  really  a  term  in  the  hourly  vectors  only,  due  to  the 
vertical  rise  and  fall  of  the  ions  from  one  stratum  to  the  other. 
On  the  other  hand  the  horizontal  and  the  vertical  components 
are  the  only  ones  which  the  terrestrial  ionic  circuits  between 
the  two  poles  will  affect,  while  the  declination  is  wholly  sub- 
ordinate.    The  rotation  of  the  sun  on  its  axis  will  in  any  event, 
whether  the  energy  is  transported  in  the  oval  polar  circuit- or 
as  a  linear  radial  radiation,  not  much  influence  the  declination 
from  day  to  day.     It  was  a  misapplication  to  assert  that  nega- 
tive results  of  the  periodogram  carry  with  them  a  decisive 
critical  meaning  regarding  any  solar  period.     This  tendency 
to  mix  up  terrestrial  and  solar  data  in  the  same  mass  of  numer- 
ical quantities,  has  been  also  found  in  the  count  of  the  num- 
ber of  the  solar  prominences,  and  is  no  doubt  to  some  extent 
unavoidable  since  in  our  common  observations  we  are  not  readily 
able  to  distinguish  between  them,  but  it  is  my  opinion  that  in 
the  present  stage  of  the  science  it  is  better  to  employ  a  simple 
comparison  of  the  data  as  they  stand  for  the  discovery  of  syn- 
chronism and  periodicity,  rather  than    to    bury  the    several 
impulses  in  one  massive  computation.     What  is  at  present 
urgently  required  in  this  research,  is  to  bring  together  all  the 
data  in  simple  homogeneous  series,  as  in  a  carefully  constructed 
ephemeris,  for  each  of  the  several  elements  of  the  entire  prob- 
lem, determine  what  is  solar  and  what  terrestrial,  and  then 
introduce  terms  in  the  functions  which  will  give  some  chance 
of  separating  the  unknowns  in  a  satisfactory  analysis.     This 
result  will  best  be  reached  by  intelligent  cooperation,  and  I 
have  no  doubt  that  practical  methods  maybe  devised  by  means 
of  which  this  purpose  can  be  accomplished.     It  seems  to  me 
a  very  important  advance  to  have  gained  a  general  view  from 


which  to  correlate  and  harmonize  so  many  of  the  problems  that 
have  heretofore  been  insoluble.  It  will,  in  conclusion,  be 
proper  to  give  some  account  of  the  instrumental  apparatus 
available  for  the  future  progress  of  the  research,  and  to  add 
after  that  a  brief  description  of  the  Mount  Weather  Observa- 
tory. 

THE    GENEEAL    ORGANIZATION    OF    THE    EESEABCH    OBSERVATORY. 

In  organizing  the  work  of  an  observatory  appropriate  to 
this  research  it  is  evident  that  the  demands  of  meteorology 
in  the  United  States  naturally  divide  its  activities  into  two 
classes. 

(a)  The  first  pertains  to  education  and  miscellaneous  minor 
problems,  and  the  second  to  the  solar-terrestrial  meteorology 
whose  object  is  to  advance  the  possibilities  of  daily  and  sea- 
sonal forecasts.  The  ordinary  collegiate  instruction  in 
meteorology  will  probably  be  limited  to  climatology  and 
elementary  principles  in  general  meteorology,  until  a  practical 
application  for  such  knowledge  can  be  found  outside  the 
activities  of  the  Government  service.  The  great  expense  of 
collecting  numerous  simultaneous  observations  will  no  doubt 
preclude  commercial  enterprises  in  that  direction,  so  that 
forecasting  in  the  United  States  will  always  be  confined  to 
the  U.  S.  Weather  Bureau.  In  large  manufacturing  plants  a 
knowledge  of  weather  conditions  is  becoming  more  essential 
to  successful  business,  so  that  a  demand  is  likely  to  arise  for 
well  trained  men  in  that  direction.  For  our  own  service  the 
exigencies  of  modern  science  are  rapidly  outgrowing  the 
capacity  of  men  unskilled  in  mathematics  and  physics  to  keep 
up  with  the  advanced  problems,  and  it  is  necessary  for  the 
Government  to  undertake  the  training  of  its  own  experts  in 
the  higher  meteorology.  The  time  is  not  far  distant  when 
each  large  city  will  require  the  presence  of  a  skilled  scientist 
in  connection  with  the  local  office,  especially  as  the  univer- 
sities are  inclined  to  cooperate  in  the  way  of  lectureships  in 
connection  with  the  courses  of  instruction  in  physics  and 
geology.  It  is  hoped  that  at  Mount  Weather  the  resident 
students  may  be  employed  as  assistants  in  the  various  lines 
of  work,  and  that  an  immediate  contact  with  the  highest  lines 
of  research  to  be  inaugurated  will  make  them  understand  and 
appreciate  the  requirements  of  physical  research  work.  A 
good  physical  laboratory  is  to  be  constructed,  the  purpose  of 
which  is  to  afford  an  opportunity  to  train  men  in  research 
methods,  and  to  investigate  the  numerous  problems  arising 
in  meteorology. 

(6)  The  second  division  of  the  work  embraces  the  opera- 
tions of  the  solar  physics  observatory,  the  magnetic  observa- 
tory, the  balloon  and  kite  plant,  and  should  be  operated  as  a 
unit,  because  the  cosmical  problem  has  branches  in  each  of 
these  realms  of  physics,  and  they  can  not  be  separated  with- 
out injuring  the  progress  that  is  to  be  expected  from  their 
cooperation.  The  primary  policy  of  this  investigation  is  to 
be  determined  by  the  fact  that  the  energy  effective  in  produ- 
cing weather  of  short  periods  and  climate  of  long  periods, 
consists  of  solar  terms  and  terrestrial  terms,  which  are  very 
closely  interwoven,  but  must  be  separated  from  each  other. 
In  the  process  of  disentangling  the  solar  and  terrestrial  terms, 
respectively,  the  functions  connecting  the  several  phenomena, 
or  the  physical  relations  between  them,  must  be  carefully 
studied.  At  present  the  entire  subject  is  in  confusion,  and 
no  deliberate  attempt  can  be  made  to  work  up  the  relative 
values  of  the  several  forces  until  the  observations  of  the  several 
kinds  are  placed  side  by  side  for  comparison.  The  establish- 
ment of  suitable  series  of  homogeneous  observations  in  the 
several  branches  is  the  first  work  of  such  an  observatory.  We 
have  so  recently  become  convinced  that  there  is  a  genuine 
solar-terrestrial  problem  for  the  meteorologist  to  investigate, 
that  but  little  definite  has  been  done  in  putting  such  a  com- 
parative work  in  operation. 


51 


The  numerous  contributions  to  the  general  subject  from  all 
portions  of  the  world  are  absolutely  bewildering  in  their  com- 
plexity, and  we  can  not  expect  to  make  any  serious  advances 
unless,  the  details  of  such  observations  can  be  classified  in  one 
far-reaching,  comprehensive  scheme.  The  observatory  must 
be  organized  like  an  army,  with  a  general  supported  by  offi- 
cers who  will  execute  the  several  parts  of  the  operations  re- 
quired in  the  plan  of  campaign.  I  shall  attempt  merely  to 
enumerate,  in  the  next  paper,  the  instrumental  methods  that 
it  is  proposed  to  employ  at  Mount  Weather,  so  far  as  experi- 
rience  shall  prove  them  to  be  practicable.  Every  stage  of  the 
instrumental  work,  and  that  of  the  reduction  of  the  observa- 


tions, will  imply  that  first-class  training  is  required,  and  of 
course  the  actual  success  of  the  enterprise  will  depend  almost 
entirely  upon  the  number  of  expert  scientists  that  can  be  pro- 
cured for  such  a  service.  As  stated  above,  the  margin  is  not 
large  upon  which  we  can  do  the  solar  work,  owing  to  the 
diminished  effects  at  the  earth  of  the  sun's  variations,  due  to 
its  great  distance  from  the  earth,  and  we  must  waste  nothing 
by  using  bad  methods  of  work  and  unskilled  men,  if  any  profit- 
able result  is  to  be  secured.  Poor  workmanship  and  untrained 
men  are  barred  by  reason  of  the  rigorous  scientific  demands 
that  are  placed  upon  these  operations  by  the  natural  physical 
conditions  which  prevail  in  cosmical  meteorology. 


YE  0087. 


UNIVERSITY  OF  CALIFORNIA  UBRARY 


